From: Jorge Mora jmora1300@gmail.com
[ 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@netapp.com Reviewed-by: Benjamin Coddington bcodding@redhat.com Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfs/nfs42.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/nfs/nfs42.h b/fs/nfs/nfs42.h index 0fe5aacbcfdf1..e7192d0eea3de 100644 --- a/fs/nfs/nfs42.h +++ b/fs/nfs/nfs42.h @@ -54,11 +54,14 @@ 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 */