This is a note to let you know that I've just added the patch titled
NFSv4.2: fix listxattr maximum XDR buffer size
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nfsv4.2-fix-listxattr-maximum-xdr-buffer-size.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ffc491fbe6e3d9c6ce54ade94834ac65dd18cc08
Author: Jorge Mora <jmora1300@xxxxxxxxx>
Date: Thu Jan 25 07:51:28 2024 -0700
NFSv4.2: fix listxattr maximum XDR buffer size
[ Upstream commit bcac8bff90a6ee1629f90669cdb9d28fb86049b0 ]
Switch order of operations to avoid creating a short XDR buffer:
e.g., buflen = 12, old xdrlen = 12, new xdrlen = 20.
Having a short XDR buffer leads to lxa_maxcount be a few bytes
less than what is needed to retrieve the whole list when using
a buflen as returned by a call with size = 0:
buflen = listxattr(path, NULL, 0);
buf = malloc(buflen);
buflen = listxattr(path, buf, buflen);
For a file with one attribute (name = '123456'), the first call
with size = 0 will return buflen = 12 ('user.123456\x00').
The second call with size = 12, sends LISTXATTRS with
lxa_maxcount = 12 + 8 (cookie) + 4 (array count) = 24. The
XDR buffer needs 8 (cookie) + 4 (array count) + 4 (name count)
+ 6 (name len) + 2 (padding) + 4 (eof) = 28 which is 4 bytes
shorter than the lxa_maxcount provided in the call.
Fixes: 04a5da690e8f ("NFSv4.2: define limits and sizes for user xattr handling")
Signed-off-by: Jorge Mora <mora@xxxxxxxxxx>
Reviewed-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/nfs/nfs42.h b/fs/nfs/nfs42.h
index b59876b01a1e3..0282d93c8bccb 100644
--- a/fs/nfs/nfs42.h
+++ b/fs/nfs/nfs42.h
@@ -55,11 +55,14 @@ int nfs42_proc_removexattr(struct inode *inode, const char *name);
* They would be 7 bytes long in the eventual buffer ("user.x\0"), and
* 8 bytes long XDR-encoded.
*
- * Include the trailing eof word as well.
+ * Include the trailing eof word as well and make the result a multiple
+ * of 4 bytes.
*/
static inline u32 nfs42_listxattr_xdrsize(u32 buflen)
{
- return ((buflen / (XATTR_USER_PREFIX_LEN + 2)) * 8) + 4;
+ u32 size = 8 * buflen / (XATTR_USER_PREFIX_LEN + 2) + 4;
+
+ return (size + 3) & ~3;
}
#endif /* CONFIG_NFS_V4_2 */
#endif /* __LINUX_FS_NFS_NFS4_2_H */
