[PATCH AUTOSEL 6.1 03/22] jfs: Fix fortify moan in symlink

Sasha Levin
2022-12-17T15:27:41Z

From: "Dr. David Alan Gilbert" <linux@treblig.org>

[ Upstream commit ebe060369f8d6e4588b115f252bebf5ba4d64350 ]

JFS has in jfs_incore.h:

/* _inline may overflow into _inline_ea when needed */
/* _inline_ea may overlay the last part of
* file._xtroot if maxentry = XTROOTINITSLOT
*/
union {
struct {
/* 128: inline symlink */
unchar _inline[128];
/* 128: inline extended attr */
unchar _inline_ea[128];
};
unchar _inline_all[256];

and currently the symlink code copies into _inline;
if this is larger than 128 bytes it triggers a fortify warning of the
form:

memcpy: detected field-spanning write (size 132) of single field
"ip->i_link" at fs/jfs/namei.c:950 (size 18446744073709551615)

when it's actually OK.

Copy it into _inline_all instead.

Reported-by: syzbot+5fc38b2ddbbca7f5c680@syzkaller.appspotmail.com
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/jfs/namei.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
index 9db4f5789c0e..4fbbf88435e6 100644
--- a/fs/jfs/namei.c
+++ b/fs/jfs/namei.c
@@ -946,7 +946,7 @@ static int jfs_symlink(struct user_namespace *mnt_userns, struct inode *dip,
if (ssize <= IDATASIZE) {
ip->i_op = &jfs_fast_symlink_inode_operations;

- ip->i_link = JFS_IP(ip)->i_inline;
+ ip->i_link = JFS_IP(ip)->i_inline_all;
memcpy(ip->i_link, name, ssize);
ip->i_size = ssize - 1;

--
2.35.1