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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells To: Steve French cc: dhowells@redhat.com, Paulo Alcantara , Shyam Prasad N , linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] cifs: Fix reacquisition of volume cookie on still-live connection Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-ID: <3756405.1712244064.1@warthog.procyon.org.uk> Date: Thu, 04 Apr 2024 16:21:04 +0100 Message-ID: <3756406.1712244064@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 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: 70431bfd825d ("cifs: Support fscache indexing rewrite") Signed-off-by: David Howells cc: Steve French cc: Paulo Alcantara cc: Shyam Prasad N cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org Acked-by: Paulo Alcantara (Red Hat) --- fs/smb/client/cifsglob.h | 2 ++ fs/smb/client/fscache.c | 13 +++++++++++++ fs/smb/client/misc.c | 3 +++ 3 files changed, 18 insertions(+) diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h index 7ed9d05f6890..43319288b4e3 100644 --- a/fs/smb/client/cifsglob.h +++ b/fs/smb/client/cifsglob.h @@ -1275,7 +1275,9 @@ 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; diff --git a/fs/smb/client/fscache.c b/fs/smb/client/fscache.c index 340efce8f052..113bde8f1e61 100644 --- a/fs/smb/client/fscache.c +++ b/fs/smb/client/fscache.c @@ -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 @@ int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon) kfree(key); out: kfree(sharename); + mutex_unlock(&tcon->fscache_lock); return ret; } diff --git a/fs/smb/client/misc.c b/fs/smb/client/misc.c index c3771fc81328..b27fbb840539 100644 --- a/fs/smb/client/misc.c +++ b/fs/smb/client/misc.c @@ -141,6 +141,9 @@ tcon_info_alloc(bool dir_leases_enabled) #ifdef CONFIG_CIFS_DFS_UPCALL INIT_LIST_HEAD(&ret_buf->dfs_ses_list); #endif +#ifdef CONFIG_CIFS_FSCACHE + mutex_init(&ret_buf->fscache_lock); +#endif return ret_buf; }