linux/fs/afs/addr_list.c
David Howells fe4d774c84 afs: Fix missing cursor clearance
afs_select_fileserver() ends the address cursor it is using in the case in
which we get some sort of network error and run out of addresses to iterate
through, before it jumps to try the next server.  This also needs to be
done when the server aborts with some sort of error that means we should
try the next server.

Fix this by:

 (1) Move the iterate_address afs_end_cursor() call to the next_server
     case.

 (2) End the cursor in the failed case.

 (3) Make afs_end_cursor() clear the ->begun flag and ->addr pointer in the
     address cursor.

 (4) Make afs_end_cursor() able to be called on an already cleared cursor.

Without this, something like the following oops may occur:

	AFS: Assertion failed
	18446612134397189888 == 0 is false
	0xffff88007c279f00 == 0x0 is false
	------------[ cut here ]------------
	kernel BUG at fs/afs/rotate.c:360!
	RIP: 0010:afs_select_fileserver+0x79b/0xa30 [kafs]
	Call Trace:
	 afs_statfs+0xcc/0x180 [kafs]
	 ? p9_client_statfs+0x9e/0x110 [9pnet]
	 ? _cond_resched+0x19/0x40
	 statfs_by_dentry+0x6d/0x90
	 vfs_statfs+0x1b/0xc0
	 user_statfs+0x4b/0x80
	 SYSC_statfs+0x15/0x30
	 SyS_statfs+0xe/0x10
	 entry_SYSCALL_64_fastpath+0x20/0x83

Fixes: d2ddc776a4 ("afs: Overhaul volume and server record caching and fileserver rotation")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: stable@vger.kernel.org
2018-02-06 14:36:54 +00:00

389 lines
8.5 KiB
C

/* Server address list management
*
* Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/dns_resolver.h>
#include <linux/inet.h>
#include <keys/rxrpc-type.h>
#include "internal.h"
#include "afs_fs.h"
//#define AFS_MAX_ADDRESSES
// ((unsigned int)((PAGE_SIZE - sizeof(struct afs_addr_list)) /
// sizeof(struct sockaddr_rxrpc)))
#define AFS_MAX_ADDRESSES ((unsigned int)(sizeof(unsigned long) * 8))
/*
* Release an address list.
*/
void afs_put_addrlist(struct afs_addr_list *alist)
{
if (alist && refcount_dec_and_test(&alist->usage))
call_rcu(&alist->rcu, (rcu_callback_t)kfree);
}
/*
* Allocate an address list.
*/
struct afs_addr_list *afs_alloc_addrlist(unsigned int nr,
unsigned short service,
unsigned short port)
{
struct afs_addr_list *alist;
unsigned int i;
_enter("%u,%u,%u", nr, service, port);
alist = kzalloc(sizeof(*alist) + sizeof(alist->addrs[0]) * nr,
GFP_KERNEL);
if (!alist)
return NULL;
refcount_set(&alist->usage, 1);
for (i = 0; i < nr; i++) {
struct sockaddr_rxrpc *srx = &alist->addrs[i];
srx->srx_family = AF_RXRPC;
srx->srx_service = service;
srx->transport_type = SOCK_DGRAM;
srx->transport_len = sizeof(srx->transport.sin6);
srx->transport.sin6.sin6_family = AF_INET6;
srx->transport.sin6.sin6_port = htons(port);
}
return alist;
}
/*
* Parse a text string consisting of delimited addresses.
*/
struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
char delim,
unsigned short service,
unsigned short port)
{
struct afs_addr_list *alist;
const char *p, *end = text + len;
unsigned int nr = 0;
_enter("%*.*s,%c", (int)len, (int)len, text, delim);
if (!len)
return ERR_PTR(-EDESTADDRREQ);
if (delim == ':' && (memchr(text, ',', len) || !memchr(text, '.', len)))
delim = ',';
/* Count the addresses */
p = text;
do {
if (!*p)
return ERR_PTR(-EINVAL);
if (*p == delim)
continue;
nr++;
if (*p == '[') {
p++;
if (p == end)
return ERR_PTR(-EINVAL);
p = memchr(p, ']', end - p);
if (!p)
return ERR_PTR(-EINVAL);
p++;
if (p >= end)
break;
}
p = memchr(p, delim, end - p);
if (!p)
break;
p++;
} while (p < end);
_debug("%u/%u addresses", nr, AFS_MAX_ADDRESSES);
if (nr > AFS_MAX_ADDRESSES)
nr = AFS_MAX_ADDRESSES;
alist = afs_alloc_addrlist(nr, service, port);
if (!alist)
return ERR_PTR(-ENOMEM);
/* Extract the addresses */
p = text;
do {
struct sockaddr_rxrpc *srx = &alist->addrs[alist->nr_addrs];
char tdelim = delim;
if (*p == delim) {
p++;
continue;
}
if (*p == '[') {
p++;
tdelim = ']';
}
if (in4_pton(p, end - p,
(u8 *)&srx->transport.sin6.sin6_addr.s6_addr32[3],
tdelim, &p)) {
srx->transport.sin6.sin6_addr.s6_addr32[0] = 0;
srx->transport.sin6.sin6_addr.s6_addr32[1] = 0;
srx->transport.sin6.sin6_addr.s6_addr32[2] = htonl(0xffff);
} else if (in6_pton(p, end - p,
srx->transport.sin6.sin6_addr.s6_addr,
tdelim, &p)) {
/* Nothing to do */
} else {
goto bad_address;
}
if (tdelim == ']') {
if (p == end || *p != ']')
goto bad_address;
p++;
}
if (p < end) {
if (*p == '+') {
/* Port number specification "+1234" */
unsigned int xport = 0;
p++;
if (p >= end || !isdigit(*p))
goto bad_address;
do {
xport *= 10;
xport += *p - '0';
if (xport > 65535)
goto bad_address;
p++;
} while (p < end && isdigit(*p));
srx->transport.sin6.sin6_port = htons(xport);
} else if (*p == delim) {
p++;
} else {
goto bad_address;
}
}
alist->nr_addrs++;
} while (p < end && alist->nr_addrs < AFS_MAX_ADDRESSES);
_leave(" = [nr %u]", alist->nr_addrs);
return alist;
bad_address:
kfree(alist);
return ERR_PTR(-EINVAL);
}
/*
* Compare old and new address lists to see if there's been any change.
* - How to do this in better than O(Nlog(N)) time?
* - We don't really want to sort the address list, but would rather take the
* list as we got it so as not to undo record rotation by the DNS server.
*/
#if 0
static int afs_cmp_addr_list(const struct afs_addr_list *a1,
const struct afs_addr_list *a2)
{
}
#endif
/*
* Perform a DNS query for VL servers and build a up an address list.
*/
struct afs_addr_list *afs_dns_query(struct afs_cell *cell, time64_t *_expiry)
{
struct afs_addr_list *alist;
char *vllist = NULL;
int ret;
_enter("%s", cell->name);
ret = dns_query("afsdb", cell->name, cell->name_len,
"ipv4", &vllist, _expiry);
if (ret < 0)
return ERR_PTR(ret);
alist = afs_parse_text_addrs(vllist, strlen(vllist), ',',
VL_SERVICE, AFS_VL_PORT);
if (IS_ERR(alist)) {
kfree(vllist);
if (alist != ERR_PTR(-ENOMEM))
pr_err("Failed to parse DNS data\n");
return alist;
}
kfree(vllist);
return alist;
}
/*
* Merge an IPv4 entry into a fileserver address list.
*/
void afs_merge_fs_addr4(struct afs_addr_list *alist, __be32 xdr, u16 port)
{
struct sockaddr_in6 *a;
__be16 xport = htons(port);
int i;
for (i = 0; i < alist->nr_ipv4; i++) {
a = &alist->addrs[i].transport.sin6;
if (xdr == a->sin6_addr.s6_addr32[3] &&
xport == a->sin6_port)
return;
if (xdr == a->sin6_addr.s6_addr32[3] &&
xport < a->sin6_port)
break;
if (xdr < a->sin6_addr.s6_addr32[3])
break;
}
if (i < alist->nr_addrs)
memmove(alist->addrs + i + 1,
alist->addrs + i,
sizeof(alist->addrs[0]) * (alist->nr_addrs - i));
a = &alist->addrs[i].transport.sin6;
a->sin6_port = xport;
a->sin6_addr.s6_addr32[0] = 0;
a->sin6_addr.s6_addr32[1] = 0;
a->sin6_addr.s6_addr32[2] = htonl(0xffff);
a->sin6_addr.s6_addr32[3] = xdr;
alist->nr_ipv4++;
alist->nr_addrs++;
}
/*
* Merge an IPv6 entry into a fileserver address list.
*/
void afs_merge_fs_addr6(struct afs_addr_list *alist, __be32 *xdr, u16 port)
{
struct sockaddr_in6 *a;
__be16 xport = htons(port);
int i, diff;
for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
a = &alist->addrs[i].transport.sin6;
diff = memcmp(xdr, &a->sin6_addr, 16);
if (diff == 0 &&
xport == a->sin6_port)
return;
if (diff == 0 &&
xport < a->sin6_port)
break;
if (diff < 0)
break;
}
if (i < alist->nr_addrs)
memmove(alist->addrs + i + 1,
alist->addrs + i,
sizeof(alist->addrs[0]) * (alist->nr_addrs - i));
a = &alist->addrs[i].transport.sin6;
a->sin6_port = xport;
a->sin6_addr.s6_addr32[0] = xdr[0];
a->sin6_addr.s6_addr32[1] = xdr[1];
a->sin6_addr.s6_addr32[2] = xdr[2];
a->sin6_addr.s6_addr32[3] = xdr[3];
alist->nr_addrs++;
}
/*
* Get an address to try.
*/
bool afs_iterate_addresses(struct afs_addr_cursor *ac)
{
_enter("%hu+%hd", ac->start, (short)ac->index);
if (!ac->alist)
return false;
if (ac->begun) {
ac->index++;
if (ac->index == ac->alist->nr_addrs)
ac->index = 0;
if (ac->index == ac->start) {
ac->error = -EDESTADDRREQ;
return false;
}
}
ac->begun = true;
ac->responded = false;
ac->addr = &ac->alist->addrs[ac->index];
return true;
}
/*
* Release an address list cursor.
*/
int afs_end_cursor(struct afs_addr_cursor *ac)
{
struct afs_addr_list *alist;
alist = ac->alist;
if (alist) {
if (ac->responded && ac->index != ac->start)
WRITE_ONCE(alist->index, ac->index);
afs_put_addrlist(alist);
}
ac->addr = NULL;
ac->alist = NULL;
ac->begun = false;
return ac->error;
}
/*
* Set the address cursor for iterating over VL servers.
*/
int afs_set_vl_cursor(struct afs_addr_cursor *ac, struct afs_cell *cell)
{
struct afs_addr_list *alist;
int ret;
if (!rcu_access_pointer(cell->vl_addrs)) {
ret = wait_on_bit(&cell->flags, AFS_CELL_FL_NO_LOOKUP_YET,
TASK_INTERRUPTIBLE);
if (ret < 0)
return ret;
if (!rcu_access_pointer(cell->vl_addrs) &&
ktime_get_real_seconds() < cell->dns_expiry)
return cell->error;
}
read_lock(&cell->vl_addrs_lock);
alist = rcu_dereference_protected(cell->vl_addrs,
lockdep_is_held(&cell->vl_addrs_lock));
if (alist->nr_addrs > 0)
afs_get_addrlist(alist);
else
alist = NULL;
read_unlock(&cell->vl_addrs_lock);
if (!alist)
return -EDESTADDRREQ;
ac->alist = alist;
ac->addr = NULL;
ac->start = READ_ONCE(alist->index);
ac->index = ac->start;
ac->error = 0;
ac->begun = false;
return 0;
}