linux/fs/splice.c
David Howells 33b3b04154 splice: Add a func to do a splice from an O_DIRECT file without ITER_PIPE
Implement a function, direct_file_splice(), that deals with this by using
an ITER_BVEC iterator instead of an ITER_PIPE iterator as the former won't
free its buffers when reverted.  The function bulk allocates all the
buffers it thinks it is going to use in advance, does the read
synchronously and only then trims the buffer down.  The pages we did use
get pushed into the pipe.

This fixes a problem with the upcoming iov_iter_extract_pages() function,
whereby pages extracted from a non-user-backed iterator such as ITER_PIPE
aren't pinned.  __iomap_dio_rw(), however, calls iov_iter_revert() to
shorten the iterator to just the bufferage it is going to use - which has
the side-effect of freeing the excess pipe buffers, even though they're
attached to a bio and may get written to by DMA (thanks to Hillf Danton for
spotting this[1]).

This then causes memory corruption that is particularly noticeable when the
syzbot test[2] is run.  The test boils down to:

	out = creat(argv[1], 0666);
	ftruncate(out, 0x800);
	lseek(out, 0x200, SEEK_SET);
	in = open(argv[1], O_RDONLY | O_DIRECT | O_NOFOLLOW);
	sendfile(out, in, NULL, 0x1dd00);

run repeatedly in parallel.  What I think is happening is that ftruncate()
occasionally shortens the DIO read that's about to be made by sendfile's
splice core by reducing i_size.

This should be more efficient for DIO read by virtue of doing a bulk page
allocation, but slightly less efficient by ignoring any partial page in the
pipe.

Reported-by: syzbot+a440341a59e3b7142895@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: David Hildenbrand <david@redhat.com>
cc: John Hubbard <jhubbard@nvidia.com>
cc: linux-mm@kvack.org
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20230207094731.1390-1-hdanton@sina.com/ [1]
Link: https://lore.kernel.org/r/000000000000b0b3c005f3a09383@google.com/ [2]
Signed-off-by: Steve French <stfrench@microsoft.com>
2023-02-20 17:25:43 -06:00

1810 lines
41 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* "splice": joining two ropes together by interweaving their strands.
*
* This is the "extended pipe" functionality, where a pipe is used as
* an arbitrary in-memory buffer. Think of a pipe as a small kernel
* buffer that you can use to transfer data from one end to the other.
*
* The traditional unix read/write is extended with a "splice()" operation
* that transfers data buffers to or from a pipe buffer.
*
* Named by Larry McVoy, original implementation from Linus, extended by
* Jens to support splicing to files, network, direct splicing, etc and
* fixing lots of bugs.
*
* Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
* Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
* Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
*
*/
#include <linux/bvec.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/splice.h>
#include <linux/memcontrol.h>
#include <linux/mm_inline.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/export.h>
#include <linux/syscalls.h>
#include <linux/uio.h>
#include <linux/security.h>
#include <linux/gfp.h>
#include <linux/socket.h>
#include <linux/sched/signal.h>
#include "internal.h"
/*
* Attempt to steal a page from a pipe buffer. This should perhaps go into
* a vm helper function, it's already simplified quite a bit by the
* addition of remove_mapping(). If success is returned, the caller may
* attempt to reuse this page for another destination.
*/
static bool page_cache_pipe_buf_try_steal(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
struct folio *folio = page_folio(buf->page);
struct address_space *mapping;
folio_lock(folio);
mapping = folio_mapping(folio);
if (mapping) {
WARN_ON(!folio_test_uptodate(folio));
/*
* At least for ext2 with nobh option, we need to wait on
* writeback completing on this folio, since we'll remove it
* from the pagecache. Otherwise truncate wont wait on the
* folio, allowing the disk blocks to be reused by someone else
* before we actually wrote our data to them. fs corruption
* ensues.
*/
folio_wait_writeback(folio);
if (folio_has_private(folio) &&
!filemap_release_folio(folio, GFP_KERNEL))
goto out_unlock;
/*
* If we succeeded in removing the mapping, set LRU flag
* and return good.
*/
if (remove_mapping(mapping, folio)) {
buf->flags |= PIPE_BUF_FLAG_LRU;
return true;
}
}
/*
* Raced with truncate or failed to remove folio from current
* address space, unlock and return failure.
*/
out_unlock:
folio_unlock(folio);
return false;
}
static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
put_page(buf->page);
buf->flags &= ~PIPE_BUF_FLAG_LRU;
}
/*
* Check whether the contents of buf is OK to access. Since the content
* is a page cache page, IO may be in flight.
*/
static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
struct page *page = buf->page;
int err;
if (!PageUptodate(page)) {
lock_page(page);
/*
* Page got truncated/unhashed. This will cause a 0-byte
* splice, if this is the first page.
*/
if (!page->mapping) {
err = -ENODATA;
goto error;
}
/*
* Uh oh, read-error from disk.
*/
if (!PageUptodate(page)) {
err = -EIO;
goto error;
}
/*
* Page is ok afterall, we are done.
*/
unlock_page(page);
}
return 0;
error:
unlock_page(page);
return err;
}
const struct pipe_buf_operations page_cache_pipe_buf_ops = {
.confirm = page_cache_pipe_buf_confirm,
.release = page_cache_pipe_buf_release,
.try_steal = page_cache_pipe_buf_try_steal,
.get = generic_pipe_buf_get,
};
static bool user_page_pipe_buf_try_steal(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
return false;
buf->flags |= PIPE_BUF_FLAG_LRU;
return generic_pipe_buf_try_steal(pipe, buf);
}
static const struct pipe_buf_operations user_page_pipe_buf_ops = {
.release = page_cache_pipe_buf_release,
.try_steal = user_page_pipe_buf_try_steal,
.get = generic_pipe_buf_get,
};
static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
{
smp_mb();
if (waitqueue_active(&pipe->rd_wait))
wake_up_interruptible(&pipe->rd_wait);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
}
/**
* splice_to_pipe - fill passed data into a pipe
* @pipe: pipe to fill
* @spd: data to fill
*
* Description:
* @spd contains a map of pages and len/offset tuples, along with
* the struct pipe_buf_operations associated with these pages. This
* function will link that data to the pipe.
*
*/
ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
struct splice_pipe_desc *spd)
{
unsigned int spd_pages = spd->nr_pages;
unsigned int tail = pipe->tail;
unsigned int head = pipe->head;
unsigned int mask = pipe->ring_size - 1;
int ret = 0, page_nr = 0;
if (!spd_pages)
return 0;
if (unlikely(!pipe->readers)) {
send_sig(SIGPIPE, current, 0);
ret = -EPIPE;
goto out;
}
while (!pipe_full(head, tail, pipe->max_usage)) {
struct pipe_buffer *buf = &pipe->bufs[head & mask];
buf->page = spd->pages[page_nr];
buf->offset = spd->partial[page_nr].offset;
buf->len = spd->partial[page_nr].len;
buf->private = spd->partial[page_nr].private;
buf->ops = spd->ops;
buf->flags = 0;
head++;
pipe->head = head;
page_nr++;
ret += buf->len;
if (!--spd->nr_pages)
break;
}
if (!ret)
ret = -EAGAIN;
out:
while (page_nr < spd_pages)
spd->spd_release(spd, page_nr++);
return ret;
}
EXPORT_SYMBOL_GPL(splice_to_pipe);
ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
{
unsigned int head = pipe->head;
unsigned int tail = pipe->tail;
unsigned int mask = pipe->ring_size - 1;
int ret;
if (unlikely(!pipe->readers)) {
send_sig(SIGPIPE, current, 0);
ret = -EPIPE;
} else if (pipe_full(head, tail, pipe->max_usage)) {
ret = -EAGAIN;
} else {
pipe->bufs[head & mask] = *buf;
pipe->head = head + 1;
return buf->len;
}
pipe_buf_release(pipe, buf);
return ret;
}
EXPORT_SYMBOL(add_to_pipe);
/*
* Check if we need to grow the arrays holding pages and partial page
* descriptions.
*/
int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
{
unsigned int max_usage = READ_ONCE(pipe->max_usage);
spd->nr_pages_max = max_usage;
if (max_usage <= PIPE_DEF_BUFFERS)
return 0;
spd->pages = kmalloc_array(max_usage, sizeof(struct page *), GFP_KERNEL);
spd->partial = kmalloc_array(max_usage, sizeof(struct partial_page),
GFP_KERNEL);
if (spd->pages && spd->partial)
return 0;
kfree(spd->pages);
kfree(spd->partial);
return -ENOMEM;
}
void splice_shrink_spd(struct splice_pipe_desc *spd)
{
if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
return;
kfree(spd->pages);
kfree(spd->partial);
}
/*
* Splice data from an O_DIRECT file into pages and then add them to the output
* pipe.
*/
ssize_t direct_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe,
size_t len, unsigned int flags)
{
struct iov_iter to;
struct bio_vec *bv;
struct kiocb kiocb;
struct page **pages;
ssize_t ret;
size_t used, npages, chunk, remain, reclaim;
int i;
/* Work out how much data we can actually add into the pipe */
used = pipe_occupancy(pipe->head, pipe->tail);
npages = max_t(ssize_t, pipe->max_usage - used, 0);
len = min_t(size_t, len, npages * PAGE_SIZE);
npages = DIV_ROUND_UP(len, PAGE_SIZE);
bv = kzalloc(array_size(npages, sizeof(bv[0])) +
array_size(npages, sizeof(struct page *)), GFP_KERNEL);
if (!bv)
return -ENOMEM;
pages = (void *)(bv + npages);
npages = alloc_pages_bulk_array(GFP_USER, npages, pages);
if (!npages) {
kfree(bv);
return -ENOMEM;
}
remain = len = min_t(size_t, len, npages * PAGE_SIZE);
for (i = 0; i < npages; i++) {
chunk = min_t(size_t, PAGE_SIZE, remain);
bv[i].bv_page = pages[i];
bv[i].bv_offset = 0;
bv[i].bv_len = chunk;
remain -= chunk;
}
/* Do the I/O */
iov_iter_bvec(&to, ITER_DEST, bv, npages, len);
init_sync_kiocb(&kiocb, in);
kiocb.ki_pos = *ppos;
ret = call_read_iter(in, &kiocb, &to);
reclaim = npages * PAGE_SIZE;
remain = 0;
if (ret > 0) {
reclaim -= ret;
remain = ret;
*ppos = kiocb.ki_pos;
file_accessed(in);
} else if (ret < 0) {
/*
* callers of ->splice_read() expect -EAGAIN on
* "can't put anything in there", rather than -EFAULT.
*/
if (ret == -EFAULT)
ret = -EAGAIN;
}
/* Free any pages that didn't get touched at all. */
reclaim /= PAGE_SIZE;
if (reclaim) {
npages -= reclaim;
release_pages(pages + npages, reclaim);
}
/* Push the remaining pages into the pipe. */
for (i = 0; i < npages; i++) {
struct pipe_buffer *buf = pipe_head_buf(pipe);
chunk = min_t(size_t, remain, PAGE_SIZE);
*buf = (struct pipe_buffer) {
.ops = &default_pipe_buf_ops,
.page = bv[i].bv_page,
.offset = 0,
.len = chunk,
};
pipe->head++;
remain -= chunk;
}
kfree(bv);
return ret;
}
/**
* generic_file_splice_read - splice data from file to a pipe
* @in: file to splice from
* @ppos: position in @in
* @pipe: pipe to splice to
* @len: number of bytes to splice
* @flags: splice modifier flags
*
* Description:
* Will read pages from given file and fill them into a pipe. Can be
* used as long as it has more or less sane ->read_iter().
*
*/
ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
struct iov_iter to;
struct kiocb kiocb;
int ret;
iov_iter_pipe(&to, ITER_DEST, pipe, len);
init_sync_kiocb(&kiocb, in);
kiocb.ki_pos = *ppos;
ret = call_read_iter(in, &kiocb, &to);
if (ret > 0) {
*ppos = kiocb.ki_pos;
file_accessed(in);
} else if (ret < 0) {
/* free what was emitted */
pipe_discard_from(pipe, to.start_head);
/*
* callers of ->splice_read() expect -EAGAIN on
* "can't put anything in there", rather than -EFAULT.
*/
if (ret == -EFAULT)
ret = -EAGAIN;
}
return ret;
}
EXPORT_SYMBOL(generic_file_splice_read);
const struct pipe_buf_operations default_pipe_buf_ops = {
.release = generic_pipe_buf_release,
.try_steal = generic_pipe_buf_try_steal,
.get = generic_pipe_buf_get,
};
/* Pipe buffer operations for a socket and similar. */
const struct pipe_buf_operations nosteal_pipe_buf_ops = {
.release = generic_pipe_buf_release,
.get = generic_pipe_buf_get,
};
EXPORT_SYMBOL(nosteal_pipe_buf_ops);
/*
* Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
* using sendpage(). Return the number of bytes sent.
*/
static int pipe_to_sendpage(struct pipe_inode_info *pipe,
struct pipe_buffer *buf, struct splice_desc *sd)
{
struct file *file = sd->u.file;
loff_t pos = sd->pos;
int more;
if (!likely(file->f_op->sendpage))
return -EINVAL;
more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
if (sd->len < sd->total_len &&
pipe_occupancy(pipe->head, pipe->tail) > 1)
more |= MSG_SENDPAGE_NOTLAST;
return file->f_op->sendpage(file, buf->page, buf->offset,
sd->len, &pos, more);
}
static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
{
smp_mb();
if (waitqueue_active(&pipe->wr_wait))
wake_up_interruptible(&pipe->wr_wait);
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
}
/**
* splice_from_pipe_feed - feed available data from a pipe to a file
* @pipe: pipe to splice from
* @sd: information to @actor
* @actor: handler that splices the data
*
* Description:
* This function loops over the pipe and calls @actor to do the
* actual moving of a single struct pipe_buffer to the desired
* destination. It returns when there's no more buffers left in
* the pipe or if the requested number of bytes (@sd->total_len)
* have been copied. It returns a positive number (one) if the
* pipe needs to be filled with more data, zero if the required
* number of bytes have been copied and -errno on error.
*
* This, together with splice_from_pipe_{begin,end,next}, may be
* used to implement the functionality of __splice_from_pipe() when
* locking is required around copying the pipe buffers to the
* destination.
*/
static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
splice_actor *actor)
{
unsigned int head = pipe->head;
unsigned int tail = pipe->tail;
unsigned int mask = pipe->ring_size - 1;
int ret;
while (!pipe_empty(head, tail)) {
struct pipe_buffer *buf = &pipe->bufs[tail & mask];
sd->len = buf->len;
if (sd->len > sd->total_len)
sd->len = sd->total_len;
ret = pipe_buf_confirm(pipe, buf);
if (unlikely(ret)) {
if (ret == -ENODATA)
ret = 0;
return ret;
}
ret = actor(pipe, buf, sd);
if (ret <= 0)
return ret;
buf->offset += ret;
buf->len -= ret;
sd->num_spliced += ret;
sd->len -= ret;
sd->pos += ret;
sd->total_len -= ret;
if (!buf->len) {
pipe_buf_release(pipe, buf);
tail++;
pipe->tail = tail;
if (pipe->files)
sd->need_wakeup = true;
}
if (!sd->total_len)
return 0;
}
return 1;
}
/* We know we have a pipe buffer, but maybe it's empty? */
static inline bool eat_empty_buffer(struct pipe_inode_info *pipe)
{
unsigned int tail = pipe->tail;
unsigned int mask = pipe->ring_size - 1;
struct pipe_buffer *buf = &pipe->bufs[tail & mask];
if (unlikely(!buf->len)) {
pipe_buf_release(pipe, buf);
pipe->tail = tail+1;
return true;
}
return false;
}
/**
* splice_from_pipe_next - wait for some data to splice from
* @pipe: pipe to splice from
* @sd: information about the splice operation
*
* Description:
* This function will wait for some data and return a positive
* value (one) if pipe buffers are available. It will return zero
* or -errno if no more data needs to be spliced.
*/
static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
{
/*
* Check for signal early to make process killable when there are
* always buffers available
*/
if (signal_pending(current))
return -ERESTARTSYS;
repeat:
while (pipe_empty(pipe->head, pipe->tail)) {
if (!pipe->writers)
return 0;
if (sd->num_spliced)
return 0;
if (sd->flags & SPLICE_F_NONBLOCK)
return -EAGAIN;
if (signal_pending(current))
return -ERESTARTSYS;
if (sd->need_wakeup) {
wakeup_pipe_writers(pipe);
sd->need_wakeup = false;
}
pipe_wait_readable(pipe);
}
if (eat_empty_buffer(pipe))
goto repeat;
return 1;
}
/**
* splice_from_pipe_begin - start splicing from pipe
* @sd: information about the splice operation
*
* Description:
* This function should be called before a loop containing
* splice_from_pipe_next() and splice_from_pipe_feed() to
* initialize the necessary fields of @sd.
*/
static void splice_from_pipe_begin(struct splice_desc *sd)
{
sd->num_spliced = 0;
sd->need_wakeup = false;
}
/**
* splice_from_pipe_end - finish splicing from pipe
* @pipe: pipe to splice from
* @sd: information about the splice operation
*
* Description:
* This function will wake up pipe writers if necessary. It should
* be called after a loop containing splice_from_pipe_next() and
* splice_from_pipe_feed().
*/
static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
{
if (sd->need_wakeup)
wakeup_pipe_writers(pipe);
}
/**
* __splice_from_pipe - splice data from a pipe to given actor
* @pipe: pipe to splice from
* @sd: information to @actor
* @actor: handler that splices the data
*
* Description:
* This function does little more than loop over the pipe and call
* @actor to do the actual moving of a single struct pipe_buffer to
* the desired destination. See pipe_to_file, pipe_to_sendpage, or
* pipe_to_user.
*
*/
ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
splice_actor *actor)
{
int ret;
splice_from_pipe_begin(sd);
do {
cond_resched();
ret = splice_from_pipe_next(pipe, sd);
if (ret > 0)
ret = splice_from_pipe_feed(pipe, sd, actor);
} while (ret > 0);
splice_from_pipe_end(pipe, sd);
return sd->num_spliced ? sd->num_spliced : ret;
}
EXPORT_SYMBOL(__splice_from_pipe);
/**
* splice_from_pipe - splice data from a pipe to a file
* @pipe: pipe to splice from
* @out: file to splice to
* @ppos: position in @out
* @len: how many bytes to splice
* @flags: splice modifier flags
* @actor: handler that splices the data
*
* Description:
* See __splice_from_pipe. This function locks the pipe inode,
* otherwise it's identical to __splice_from_pipe().
*
*/
ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
loff_t *ppos, size_t len, unsigned int flags,
splice_actor *actor)
{
ssize_t ret;
struct splice_desc sd = {
.total_len = len,
.flags = flags,
.pos = *ppos,
.u.file = out,
};
pipe_lock(pipe);
ret = __splice_from_pipe(pipe, &sd, actor);
pipe_unlock(pipe);
return ret;
}
/**
* iter_file_splice_write - splice data from a pipe to a file
* @pipe: pipe info
* @out: file to write to
* @ppos: position in @out
* @len: number of bytes to splice
* @flags: splice modifier flags
*
* Description:
* Will either move or copy pages (determined by @flags options) from
* the given pipe inode to the given file.
* This one is ->write_iter-based.
*
*/
ssize_t
iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
loff_t *ppos, size_t len, unsigned int flags)
{
struct splice_desc sd = {
.total_len = len,
.flags = flags,
.pos = *ppos,
.u.file = out,
};
int nbufs = pipe->max_usage;
struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
GFP_KERNEL);
ssize_t ret;
if (unlikely(!array))
return -ENOMEM;
pipe_lock(pipe);
splice_from_pipe_begin(&sd);
while (sd.total_len) {
struct iov_iter from;
unsigned int head, tail, mask;
size_t left;
int n;
ret = splice_from_pipe_next(pipe, &sd);
if (ret <= 0)
break;
if (unlikely(nbufs < pipe->max_usage)) {
kfree(array);
nbufs = pipe->max_usage;
array = kcalloc(nbufs, sizeof(struct bio_vec),
GFP_KERNEL);
if (!array) {
ret = -ENOMEM;
break;
}
}
head = pipe->head;
tail = pipe->tail;
mask = pipe->ring_size - 1;
/* build the vector */
left = sd.total_len;
for (n = 0; !pipe_empty(head, tail) && left && n < nbufs; tail++) {
struct pipe_buffer *buf = &pipe->bufs[tail & mask];
size_t this_len = buf->len;
/* zero-length bvecs are not supported, skip them */
if (!this_len)
continue;
this_len = min(this_len, left);
ret = pipe_buf_confirm(pipe, buf);
if (unlikely(ret)) {
if (ret == -ENODATA)
ret = 0;
goto done;
}
array[n].bv_page = buf->page;
array[n].bv_len = this_len;
array[n].bv_offset = buf->offset;
left -= this_len;
n++;
}
iov_iter_bvec(&from, ITER_SOURCE, array, n, sd.total_len - left);
ret = vfs_iter_write(out, &from, &sd.pos, 0);
if (ret <= 0)
break;
sd.num_spliced += ret;
sd.total_len -= ret;
*ppos = sd.pos;
/* dismiss the fully eaten buffers, adjust the partial one */
tail = pipe->tail;
while (ret) {
struct pipe_buffer *buf = &pipe->bufs[tail & mask];
if (ret >= buf->len) {
ret -= buf->len;
buf->len = 0;
pipe_buf_release(pipe, buf);
tail++;
pipe->tail = tail;
if (pipe->files)
sd.need_wakeup = true;
} else {
buf->offset += ret;
buf->len -= ret;
ret = 0;
}
}
}
done:
kfree(array);
splice_from_pipe_end(pipe, &sd);
pipe_unlock(pipe);
if (sd.num_spliced)
ret = sd.num_spliced;
return ret;
}
EXPORT_SYMBOL(iter_file_splice_write);
/**
* generic_splice_sendpage - splice data from a pipe to a socket
* @pipe: pipe to splice from
* @out: socket to write to
* @ppos: position in @out
* @len: number of bytes to splice
* @flags: splice modifier flags
*
* Description:
* Will send @len bytes from the pipe to a network socket. No data copying
* is involved.
*
*/
ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
loff_t *ppos, size_t len, unsigned int flags)
{
return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
}
EXPORT_SYMBOL(generic_splice_sendpage);
static int warn_unsupported(struct file *file, const char *op)
{
pr_debug_ratelimited(
"splice %s not supported for file %pD4 (pid: %d comm: %.20s)\n",
op, file, current->pid, current->comm);
return -EINVAL;
}
/*
* Attempt to initiate a splice from pipe to file.
*/
static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
loff_t *ppos, size_t len, unsigned int flags)
{
if (unlikely(!out->f_op->splice_write))
return warn_unsupported(out, "write");
return out->f_op->splice_write(pipe, out, ppos, len, flags);
}
/*
* Attempt to initiate a splice from a file to a pipe.
*/
static long do_splice_to(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
unsigned int p_space;
int ret;
if (unlikely(!(in->f_mode & FMODE_READ)))
return -EBADF;
/* Don't try to read more the pipe has space for. */
p_space = pipe->max_usage - pipe_occupancy(pipe->head, pipe->tail);
len = min_t(size_t, len, p_space << PAGE_SHIFT);
ret = rw_verify_area(READ, in, ppos, len);
if (unlikely(ret < 0))
return ret;
if (unlikely(len > MAX_RW_COUNT))
len = MAX_RW_COUNT;
if (unlikely(!in->f_op->splice_read))
return warn_unsupported(in, "read");
return in->f_op->splice_read(in, ppos, pipe, len, flags);
}
/**
* splice_direct_to_actor - splices data directly between two non-pipes
* @in: file to splice from
* @sd: actor information on where to splice to
* @actor: handles the data splicing
*
* Description:
* This is a special case helper to splice directly between two
* points, without requiring an explicit pipe. Internally an allocated
* pipe is cached in the process, and reused during the lifetime of
* that process.
*
*/
ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
splice_direct_actor *actor)
{
struct pipe_inode_info *pipe;
long ret, bytes;
size_t len;
int i, flags, more;
/*
* We require the input to be seekable, as we don't want to randomly
* drop data for eg socket -> socket splicing. Use the piped splicing
* for that!
*/
if (unlikely(!(in->f_mode & FMODE_LSEEK)))
return -EINVAL;
/*
* neither in nor out is a pipe, setup an internal pipe attached to
* 'out' and transfer the wanted data from 'in' to 'out' through that
*/
pipe = current->splice_pipe;
if (unlikely(!pipe)) {
pipe = alloc_pipe_info();
if (!pipe)
return -ENOMEM;
/*
* We don't have an immediate reader, but we'll read the stuff
* out of the pipe right after the splice_to_pipe(). So set
* PIPE_READERS appropriately.
*/
pipe->readers = 1;
current->splice_pipe = pipe;
}
/*
* Do the splice.
*/
ret = 0;
bytes = 0;
len = sd->total_len;
flags = sd->flags;
/*
* Don't block on output, we have to drain the direct pipe.
*/
sd->flags &= ~SPLICE_F_NONBLOCK;
more = sd->flags & SPLICE_F_MORE;
WARN_ON_ONCE(!pipe_empty(pipe->head, pipe->tail));
while (len) {
size_t read_len;
loff_t pos = sd->pos, prev_pos = pos;
ret = do_splice_to(in, &pos, pipe, len, flags);
if (unlikely(ret <= 0))
goto out_release;
read_len = ret;
sd->total_len = read_len;
/*
* If more data is pending, set SPLICE_F_MORE
* If this is the last data and SPLICE_F_MORE was not set
* initially, clears it.
*/
if (read_len < len)
sd->flags |= SPLICE_F_MORE;
else if (!more)
sd->flags &= ~SPLICE_F_MORE;
/*
* NOTE: nonblocking mode only applies to the input. We
* must not do the output in nonblocking mode as then we
* could get stuck data in the internal pipe:
*/
ret = actor(pipe, sd);
if (unlikely(ret <= 0)) {
sd->pos = prev_pos;
goto out_release;
}
bytes += ret;
len -= ret;
sd->pos = pos;
if (ret < read_len) {
sd->pos = prev_pos + ret;
goto out_release;
}
}
done:
pipe->tail = pipe->head = 0;
file_accessed(in);
return bytes;
out_release:
/*
* If we did an incomplete transfer we must release
* the pipe buffers in question:
*/
for (i = 0; i < pipe->ring_size; i++) {
struct pipe_buffer *buf = &pipe->bufs[i];
if (buf->ops)
pipe_buf_release(pipe, buf);
}
if (!bytes)
bytes = ret;
goto done;
}
EXPORT_SYMBOL(splice_direct_to_actor);
static int direct_splice_actor(struct pipe_inode_info *pipe,
struct splice_desc *sd)
{
struct file *file = sd->u.file;
return do_splice_from(pipe, file, sd->opos, sd->total_len,
sd->flags);
}
/**
* do_splice_direct - splices data directly between two files
* @in: file to splice from
* @ppos: input file offset
* @out: file to splice to
* @opos: output file offset
* @len: number of bytes to splice
* @flags: splice modifier flags
*
* Description:
* For use by do_sendfile(). splice can easily emulate sendfile, but
* doing it in the application would incur an extra system call
* (splice in + splice out, as compared to just sendfile()). So this helper
* can splice directly through a process-private pipe.
*
*/
long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
loff_t *opos, size_t len, unsigned int flags)
{
struct splice_desc sd = {
.len = len,
.total_len = len,
.flags = flags,
.pos = *ppos,
.u.file = out,
.opos = opos,
};
long ret;
if (unlikely(!(out->f_mode & FMODE_WRITE)))
return -EBADF;
if (unlikely(out->f_flags & O_APPEND))
return -EINVAL;
ret = rw_verify_area(WRITE, out, opos, len);
if (unlikely(ret < 0))
return ret;
ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
if (ret > 0)
*ppos = sd.pos;
return ret;
}
EXPORT_SYMBOL(do_splice_direct);
static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
{
for (;;) {
if (unlikely(!pipe->readers)) {
send_sig(SIGPIPE, current, 0);
return -EPIPE;
}
if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
return 0;
if (flags & SPLICE_F_NONBLOCK)
return -EAGAIN;
if (signal_pending(current))
return -ERESTARTSYS;
pipe_wait_writable(pipe);
}
}
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
struct pipe_inode_info *opipe,
size_t len, unsigned int flags);
long splice_file_to_pipe(struct file *in,
struct pipe_inode_info *opipe,
loff_t *offset,
size_t len, unsigned int flags)
{
long ret;
pipe_lock(opipe);
ret = wait_for_space(opipe, flags);
if (!ret)
ret = do_splice_to(in, offset, opipe, len, flags);
pipe_unlock(opipe);
if (ret > 0)
wakeup_pipe_readers(opipe);
return ret;
}
/*
* Determine where to splice to/from.
*/
long do_splice(struct file *in, loff_t *off_in, struct file *out,
loff_t *off_out, size_t len, unsigned int flags)
{
struct pipe_inode_info *ipipe;
struct pipe_inode_info *opipe;
loff_t offset;
long ret;
if (unlikely(!(in->f_mode & FMODE_READ) ||
!(out->f_mode & FMODE_WRITE)))
return -EBADF;
ipipe = get_pipe_info(in, true);
opipe = get_pipe_info(out, true);
if (ipipe && opipe) {
if (off_in || off_out)
return -ESPIPE;
/* Splicing to self would be fun, but... */
if (ipipe == opipe)
return -EINVAL;
if ((in->f_flags | out->f_flags) & O_NONBLOCK)
flags |= SPLICE_F_NONBLOCK;
return splice_pipe_to_pipe(ipipe, opipe, len, flags);
}
if (ipipe) {
if (off_in)
return -ESPIPE;
if (off_out) {
if (!(out->f_mode & FMODE_PWRITE))
return -EINVAL;
offset = *off_out;
} else {
offset = out->f_pos;
}
if (unlikely(out->f_flags & O_APPEND))
return -EINVAL;
ret = rw_verify_area(WRITE, out, &offset, len);
if (unlikely(ret < 0))
return ret;
if (in->f_flags & O_NONBLOCK)
flags |= SPLICE_F_NONBLOCK;
file_start_write(out);
ret = do_splice_from(ipipe, out, &offset, len, flags);
file_end_write(out);
if (!off_out)
out->f_pos = offset;
else
*off_out = offset;
return ret;
}
if (opipe) {
if (off_out)
return -ESPIPE;
if (off_in) {
if (!(in->f_mode & FMODE_PREAD))
return -EINVAL;
offset = *off_in;
} else {
offset = in->f_pos;
}
if (out->f_flags & O_NONBLOCK)
flags |= SPLICE_F_NONBLOCK;
ret = splice_file_to_pipe(in, opipe, &offset, len, flags);
if (!off_in)
in->f_pos = offset;
else
*off_in = offset;
return ret;
}
return -EINVAL;
}
static long __do_splice(struct file *in, loff_t __user *off_in,
struct file *out, loff_t __user *off_out,
size_t len, unsigned int flags)
{
struct pipe_inode_info *ipipe;
struct pipe_inode_info *opipe;
loff_t offset, *__off_in = NULL, *__off_out = NULL;
long ret;
ipipe = get_pipe_info(in, true);
opipe = get_pipe_info(out, true);
if (ipipe && off_in)
return -ESPIPE;
if (opipe && off_out)
return -ESPIPE;
if (off_out) {
if (copy_from_user(&offset, off_out, sizeof(loff_t)))
return -EFAULT;
__off_out = &offset;
}
if (off_in) {
if (copy_from_user(&offset, off_in, sizeof(loff_t)))
return -EFAULT;
__off_in = &offset;
}
ret = do_splice(in, __off_in, out, __off_out, len, flags);
if (ret < 0)
return ret;
if (__off_out && copy_to_user(off_out, __off_out, sizeof(loff_t)))
return -EFAULT;
if (__off_in && copy_to_user(off_in, __off_in, sizeof(loff_t)))
return -EFAULT;
return ret;
}
static int iter_to_pipe(struct iov_iter *from,
struct pipe_inode_info *pipe,
unsigned flags)
{
struct pipe_buffer buf = {
.ops = &user_page_pipe_buf_ops,
.flags = flags
};
size_t total = 0;
int ret = 0;
while (iov_iter_count(from)) {
struct page *pages[16];
ssize_t left;
size_t start;
int i, n;
left = iov_iter_get_pages2(from, pages, ~0UL, 16, &start);
if (left <= 0) {
ret = left;
break;
}
n = DIV_ROUND_UP(left + start, PAGE_SIZE);
for (i = 0; i < n; i++) {
int size = min_t(int, left, PAGE_SIZE - start);
buf.page = pages[i];
buf.offset = start;
buf.len = size;
ret = add_to_pipe(pipe, &buf);
if (unlikely(ret < 0)) {
iov_iter_revert(from, left);
// this one got dropped by add_to_pipe()
while (++i < n)
put_page(pages[i]);
goto out;
}
total += ret;
left -= size;
start = 0;
}
}
out:
return total ? total : ret;
}
static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
struct splice_desc *sd)
{
int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
return n == sd->len ? n : -EFAULT;
}
/*
* For lack of a better implementation, implement vmsplice() to userspace
* as a simple copy of the pipes pages to the user iov.
*/
static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
unsigned int flags)
{
struct pipe_inode_info *pipe = get_pipe_info(file, true);
struct splice_desc sd = {
.total_len = iov_iter_count(iter),
.flags = flags,
.u.data = iter
};
long ret = 0;
if (!pipe)
return -EBADF;
if (sd.total_len) {
pipe_lock(pipe);
ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
pipe_unlock(pipe);
}
return ret;
}
/*
* vmsplice splices a user address range into a pipe. It can be thought of
* as splice-from-memory, where the regular splice is splice-from-file (or
* to file). In both cases the output is a pipe, naturally.
*/
static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
unsigned int flags)
{
struct pipe_inode_info *pipe;
long ret = 0;
unsigned buf_flag = 0;
if (flags & SPLICE_F_GIFT)
buf_flag = PIPE_BUF_FLAG_GIFT;
pipe = get_pipe_info(file, true);
if (!pipe)
return -EBADF;
pipe_lock(pipe);
ret = wait_for_space(pipe, flags);
if (!ret)
ret = iter_to_pipe(iter, pipe, buf_flag);
pipe_unlock(pipe);
if (ret > 0)
wakeup_pipe_readers(pipe);
return ret;
}
static int vmsplice_type(struct fd f, int *type)
{
if (!f.file)
return -EBADF;
if (f.file->f_mode & FMODE_WRITE) {
*type = ITER_SOURCE;
} else if (f.file->f_mode & FMODE_READ) {
*type = ITER_DEST;
} else {
fdput(f);
return -EBADF;
}
return 0;
}
/*
* Note that vmsplice only really supports true splicing _from_ user memory
* to a pipe, not the other way around. Splicing from user memory is a simple
* operation that can be supported without any funky alignment restrictions
* or nasty vm tricks. We simply map in the user memory and fill them into
* a pipe. The reverse isn't quite as easy, though. There are two possible
* solutions for that:
*
* - memcpy() the data internally, at which point we might as well just
* do a regular read() on the buffer anyway.
* - Lots of nasty vm tricks, that are neither fast nor flexible (it
* has restriction limitations on both ends of the pipe).
*
* Currently we punt and implement it as a normal copy, see pipe_to_user().
*
*/
SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
unsigned long, nr_segs, unsigned int, flags)
{
struct iovec iovstack[UIO_FASTIOV];
struct iovec *iov = iovstack;
struct iov_iter iter;
ssize_t error;
struct fd f;
int type;
if (unlikely(flags & ~SPLICE_F_ALL))
return -EINVAL;
f = fdget(fd);
error = vmsplice_type(f, &type);
if (error)
return error;
error = import_iovec(type, uiov, nr_segs,
ARRAY_SIZE(iovstack), &iov, &iter);
if (error < 0)
goto out_fdput;
if (!iov_iter_count(&iter))
error = 0;
else if (type == ITER_SOURCE)
error = vmsplice_to_pipe(f.file, &iter, flags);
else
error = vmsplice_to_user(f.file, &iter, flags);
kfree(iov);
out_fdput:
fdput(f);
return error;
}
SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
int, fd_out, loff_t __user *, off_out,
size_t, len, unsigned int, flags)
{
struct fd in, out;
long error;
if (unlikely(!len))
return 0;
if (unlikely(flags & ~SPLICE_F_ALL))
return -EINVAL;
error = -EBADF;
in = fdget(fd_in);
if (in.file) {
out = fdget(fd_out);
if (out.file) {
error = __do_splice(in.file, off_in, out.file, off_out,
len, flags);
fdput(out);
}
fdput(in);
}
return error;
}
/*
* Make sure there's data to read. Wait for input if we can, otherwise
* return an appropriate error.
*/
static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
{
int ret;
/*
* Check the pipe occupancy without the inode lock first. This function
* is speculative anyways, so missing one is ok.
*/
if (!pipe_empty(pipe->head, pipe->tail))
return 0;
ret = 0;
pipe_lock(pipe);
while (pipe_empty(pipe->head, pipe->tail)) {
if (signal_pending(current)) {
ret = -ERESTARTSYS;
break;
}
if (!pipe->writers)
break;
if (flags & SPLICE_F_NONBLOCK) {
ret = -EAGAIN;
break;
}
pipe_wait_readable(pipe);
}
pipe_unlock(pipe);
return ret;
}
/*
* Make sure there's writeable room. Wait for room if we can, otherwise
* return an appropriate error.
*/
static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
{
int ret;
/*
* Check pipe occupancy without the inode lock first. This function
* is speculative anyways, so missing one is ok.
*/
if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
return 0;
ret = 0;
pipe_lock(pipe);
while (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
if (!pipe->readers) {
send_sig(SIGPIPE, current, 0);
ret = -EPIPE;
break;
}
if (flags & SPLICE_F_NONBLOCK) {
ret = -EAGAIN;
break;
}
if (signal_pending(current)) {
ret = -ERESTARTSYS;
break;
}
pipe_wait_writable(pipe);
}
pipe_unlock(pipe);
return ret;
}
/*
* Splice contents of ipipe to opipe.
*/
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
struct pipe_inode_info *opipe,
size_t len, unsigned int flags)
{
struct pipe_buffer *ibuf, *obuf;
unsigned int i_head, o_head;
unsigned int i_tail, o_tail;
unsigned int i_mask, o_mask;
int ret = 0;
bool input_wakeup = false;
retry:
ret = ipipe_prep(ipipe, flags);
if (ret)
return ret;
ret = opipe_prep(opipe, flags);
if (ret)
return ret;
/*
* Potential ABBA deadlock, work around it by ordering lock
* grabbing by pipe info address. Otherwise two different processes
* could deadlock (one doing tee from A -> B, the other from B -> A).
*/
pipe_double_lock(ipipe, opipe);
i_tail = ipipe->tail;
i_mask = ipipe->ring_size - 1;
o_head = opipe->head;
o_mask = opipe->ring_size - 1;
do {
size_t o_len;
if (!opipe->readers) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
break;
}
i_head = ipipe->head;
o_tail = opipe->tail;
if (pipe_empty(i_head, i_tail) && !ipipe->writers)
break;
/*
* Cannot make any progress, because either the input
* pipe is empty or the output pipe is full.
*/
if (pipe_empty(i_head, i_tail) ||
pipe_full(o_head, o_tail, opipe->max_usage)) {
/* Already processed some buffers, break */
if (ret)
break;
if (flags & SPLICE_F_NONBLOCK) {
ret = -EAGAIN;
break;
}
/*
* We raced with another reader/writer and haven't
* managed to process any buffers. A zero return
* value means EOF, so retry instead.
*/
pipe_unlock(ipipe);
pipe_unlock(opipe);
goto retry;
}
ibuf = &ipipe->bufs[i_tail & i_mask];
obuf = &opipe->bufs[o_head & o_mask];
if (len >= ibuf->len) {
/*
* Simply move the whole buffer from ipipe to opipe
*/
*obuf = *ibuf;
ibuf->ops = NULL;
i_tail++;
ipipe->tail = i_tail;
input_wakeup = true;
o_len = obuf->len;
o_head++;
opipe->head = o_head;
} else {
/*
* Get a reference to this pipe buffer,
* so we can copy the contents over.
*/
if (!pipe_buf_get(ipipe, ibuf)) {
if (ret == 0)
ret = -EFAULT;
break;
}
*obuf = *ibuf;
/*
* Don't inherit the gift and merge flags, we need to
* prevent multiple steals of this page.
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
obuf->len = len;
ibuf->offset += len;
ibuf->len -= len;
o_len = len;
o_head++;
opipe->head = o_head;
}
ret += o_len;
len -= o_len;
} while (len);
pipe_unlock(ipipe);
pipe_unlock(opipe);
/*
* If we put data in the output pipe, wakeup any potential readers.
*/
if (ret > 0)
wakeup_pipe_readers(opipe);
if (input_wakeup)
wakeup_pipe_writers(ipipe);
return ret;
}
/*
* Link contents of ipipe to opipe.
*/
static int link_pipe(struct pipe_inode_info *ipipe,
struct pipe_inode_info *opipe,
size_t len, unsigned int flags)
{
struct pipe_buffer *ibuf, *obuf;
unsigned int i_head, o_head;
unsigned int i_tail, o_tail;
unsigned int i_mask, o_mask;
int ret = 0;
/*
* Potential ABBA deadlock, work around it by ordering lock
* grabbing by pipe info address. Otherwise two different processes
* could deadlock (one doing tee from A -> B, the other from B -> A).
*/
pipe_double_lock(ipipe, opipe);
i_tail = ipipe->tail;
i_mask = ipipe->ring_size - 1;
o_head = opipe->head;
o_mask = opipe->ring_size - 1;
do {
if (!opipe->readers) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
break;
}
i_head = ipipe->head;
o_tail = opipe->tail;
/*
* If we have iterated all input buffers or run out of
* output room, break.
*/
if (pipe_empty(i_head, i_tail) ||
pipe_full(o_head, o_tail, opipe->max_usage))
break;
ibuf = &ipipe->bufs[i_tail & i_mask];
obuf = &opipe->bufs[o_head & o_mask];
/*
* Get a reference to this pipe buffer,
* so we can copy the contents over.
*/
if (!pipe_buf_get(ipipe, ibuf)) {
if (ret == 0)
ret = -EFAULT;
break;
}
*obuf = *ibuf;
/*
* Don't inherit the gift and merge flag, we need to prevent
* multiple steals of this page.
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
if (obuf->len > len)
obuf->len = len;
ret += obuf->len;
len -= obuf->len;
o_head++;
opipe->head = o_head;
i_tail++;
} while (len);
pipe_unlock(ipipe);
pipe_unlock(opipe);
/*
* If we put data in the output pipe, wakeup any potential readers.
*/
if (ret > 0)
wakeup_pipe_readers(opipe);
return ret;
}
/*
* This is a tee(1) implementation that works on pipes. It doesn't copy
* any data, it simply references the 'in' pages on the 'out' pipe.
* The 'flags' used are the SPLICE_F_* variants, currently the only
* applicable one is SPLICE_F_NONBLOCK.
*/
long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
{
struct pipe_inode_info *ipipe = get_pipe_info(in, true);
struct pipe_inode_info *opipe = get_pipe_info(out, true);
int ret = -EINVAL;
if (unlikely(!(in->f_mode & FMODE_READ) ||
!(out->f_mode & FMODE_WRITE)))
return -EBADF;
/*
* Duplicate the contents of ipipe to opipe without actually
* copying the data.
*/
if (ipipe && opipe && ipipe != opipe) {
if ((in->f_flags | out->f_flags) & O_NONBLOCK)
flags |= SPLICE_F_NONBLOCK;
/*
* Keep going, unless we encounter an error. The ipipe/opipe
* ordering doesn't really matter.
*/
ret = ipipe_prep(ipipe, flags);
if (!ret) {
ret = opipe_prep(opipe, flags);
if (!ret)
ret = link_pipe(ipipe, opipe, len, flags);
}
}
return ret;
}
SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
{
struct fd in, out;
int error;
if (unlikely(flags & ~SPLICE_F_ALL))
return -EINVAL;
if (unlikely(!len))
return 0;
error = -EBADF;
in = fdget(fdin);
if (in.file) {
out = fdget(fdout);
if (out.file) {
error = do_tee(in.file, out.file, len, flags);
fdput(out);
}
fdput(in);
}
return error;
}