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cifs: Fix locking in cifs_strict_readv()

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Fix to take the i_rwsem (through the netfs locking wrappers) before taking
cinode->lock_sem.

Fixes: 3ee1a1fc39 ("cifs: Cut over to using netfslib")
Reported-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Steve French 2024-05-13 17:02:05 -05:00
parent 29b4c7bb85
commit 14b1cd2534
4 changed files with 29 additions and 10 deletions
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3
fs/netfs/direct_read.c
View file

@ -26,7 +26,7 @@
*
* The caller must hold any appropriate locks.
*/
static ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter)
ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter)
{
struct netfs_io_request *rreq;
ssize_t ret;
@ -98,6 +98,7 @@ static ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_
iov_iter_revert(iter, orig_count - iov_iter_count(iter));
return ret;
}
EXPORT_SYMBOL(netfs_unbuffered_read_iter_locked);
/**
* netfs_unbuffered_read_iter - Perform an unbuffered or direct I/O read

1
fs/smb/client/cifsglob.h
View file

@ -1995,6 +1995,7 @@ require use of the stronger protocol */
* ->chans_need_reconnect
* ->chans_in_reconnect
* cifs_tcon->tc_lock (anything that is not protected by another lock and can change)
* inode->i_rwsem, taken by fs/netfs/locking.c e.g. should be taken before cifsInodeInfo locks
* cifsInodeInfo->open_file_lock cifsInodeInfo->openFileList cifs_alloc_inode
* cifsInodeInfo->writers_lock cifsInodeInfo->writers cifsInodeInfo_alloc
* cifsInodeInfo->lock_sem cifsInodeInfo->llist cifs_init_once

34
fs/smb/client/file.c
View file

@ -2916,16 +2916,32 @@ cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to)
* We need to hold the sem to be sure nobody modifies lock list
* with a brlock that prevents reading.
*/
down_read(&cinode->lock_sem);
if (!cifs_find_lock_conflict(cfile, iocb->ki_pos, iov_iter_count(to),
tcon->ses->server->vals->shared_lock_type,
0, NULL, CIFS_READ_OP)) {
if (iocb->ki_flags & IOCB_DIRECT)
rc = netfs_unbuffered_read_iter(iocb, to);
else
rc = netfs_buffered_read_iter(iocb, to);
if (iocb->ki_flags & IOCB_DIRECT) {
rc = netfs_start_io_direct(inode);
if (rc < 0)
goto out;
down_read(&cinode->lock_sem);
if (!cifs_find_lock_conflict(
cfile, iocb->ki_pos, iov_iter_count(to),
tcon->ses->server->vals->shared_lock_type,
0, NULL, CIFS_READ_OP))
rc = netfs_unbuffered_read_iter_locked(iocb, to);
up_read(&cinode->lock_sem);
netfs_end_io_direct(inode);
} else {
rc = netfs_start_io_read(inode);
if (rc < 0)
goto out;
down_read(&cinode->lock_sem);
if (!cifs_find_lock_conflict(
cfile, iocb->ki_pos, iov_iter_count(to),
tcon->ses->server->vals->shared_lock_type,
0, NULL, CIFS_READ_OP))
rc = filemap_read(iocb, to, 0);
up_read(&cinode->lock_sem);
netfs_end_io_read(inode);
}
up_read(&cinode->lock_sem);
out:
return rc;
}

1
include/linux/netfs.h
View file

@ -389,6 +389,7 @@ struct netfs_cache_ops {
};
/* High-level read API. */
ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_buffered_read_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter);