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cifs: Fix reacquisition of volume cookie on still-live connection

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During mount, cifs_mount_get_tcon() gets a tcon resource connection record
and then attaches an fscache volume cookie to it.  However, it does this
irrespective of whether or not the tcon returned from cifs_get_tcon() is a
new record or one that's already in use.  This leads to a warning about a
volume cookie collision and a leaked volume cookie because tcon->fscache
gets reset.

Fix this be adding a mutex and a "we've already tried this" flag and only
doing it once for the lifetime of the tcon.

[!] Note: Looking at cifs_mount_get_tcon(), a more general solution may
actually be required.  Reacquiring the volume cookie isn't the only thing
that function does: it also partially reinitialises the tcon record without
any locking - which may cause live filesystem ops already using the tcon
through a previous mount to malfunction.

This can be reproduced simply by something like:

    mount //example.com/test /xfstest.test -o user=shares,pass=xxx,fsc
    mount //example.com/test /mnt -o user=shares,pass=xxx,fsc

Fixes: 70431bfd82 ("cifs: Support fscache indexing rewrite")
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
cc: Shyam Prasad N <sprasad@microsoft.com>
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
David Howells 2024-04-04 16:05:19 +01:00 committed by Steve French
parent 0bbac3facb
commit dad80c6bff
3 changed files with 18 additions and 0 deletions
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2
fs/smb/client/cifsglob.h
View File

@ -1276,7 +1276,9 @@ struct cifs_tcon {
__u32 max_cached_dirs;
#ifdef CONFIG_CIFS_FSCACHE
u64 resource_id; /* server resource id */
bool fscache_acquired; /* T if we've tried acquiring a cookie */
struct fscache_volume *fscache; /* cookie for share */
struct mutex fscache_lock; /* Prevent regetting a cookie */
#endif
struct list_head pending_opens; /* list of incomplete opens */
struct cached_fids *cfids;

13
fs/smb/client/fscache.c
View File

@ -43,12 +43,23 @@ int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon)
char *key;
int ret = -ENOMEM;
if (tcon->fscache_acquired)
return 0;
mutex_lock(&tcon->fscache_lock);
if (tcon->fscache_acquired) {
mutex_unlock(&tcon->fscache_lock);
return 0;
}
tcon->fscache_acquired = true;
tcon->fscache = NULL;
switch (sa->sa_family) {
case AF_INET:
case AF_INET6:
break;
default:
mutex_unlock(&tcon->fscache_lock);
cifs_dbg(VFS, "Unknown network family '%d'\n", sa->sa_family);
return -EINVAL;
}
@ -57,6 +68,7 @@ int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon)
sharename = extract_sharename(tcon->tree_name);
if (IS_ERR(sharename)) {
mutex_unlock(&tcon->fscache_lock);
cifs_dbg(FYI, "%s: couldn't extract sharename\n", __func__);
return PTR_ERR(sharename);
}
@ -90,6 +102,7 @@ out_2:
kfree(key);
out:
kfree(sharename);
mutex_unlock(&tcon->fscache_lock);
return ret;
}

3
fs/smb/client/misc.c
View File

@ -139,6 +139,9 @@ tcon_info_alloc(bool dir_leases_enabled)
atomic_set(&ret_buf->num_local_opens, 0);
atomic_set(&ret_buf->num_remote_opens, 0);
ret_buf->stats_from_time = ktime_get_real_seconds();
#ifdef CONFIG_CIFS_FSCACHE
mutex_init(&ret_buf->fscache_lock);
#endif
return ret_buf;
}