linux-kernel - [PATCH AUTOSEL 6.8 01/18] fs/9p: only translate RWX permissions for plain 9P2000

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Date: Tue, 23 Apr 2024 07:00:57 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Joakim Sindholt <opensource@...sha.com>,
	Eric Van Hensbergen <ericvh@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	lucho@...kov.net,
	asmadeus@...ewreck.org,
	v9fs@...ts.linux.dev
Subject: [PATCH AUTOSEL 6.8 01/18] fs/9p: only translate RWX permissions for plain 9P2000

From: Joakim Sindholt <opensource@...sha.com>

[ Upstream commit cd25e15e57e68a6b18dc9323047fe9c68b99290b ]

Garbage in plain 9P2000's perm bits is allowed through, which causes it
to be able to set (among others) the suid bit. This was presumably not
the intent since the unix extended bits are handled explicitly and
conditionally on .u.

Signed-off-by: Joakim Sindholt <opensource@...sha.com>
Signed-off-by: Eric Van Hensbergen <ericvh@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/9p/vfs_inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 32572982f72e6..e337fec9b18e1 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -83,7 +83,7 @@ static int p9mode2perm(struct v9fs_session_info *v9ses,
 	int res;
 	int mode = stat->mode;
 
-	res = mode & S_IALLUGO;
+	res = mode & 0777; /* S_IRWXUGO */
 	if (v9fs_proto_dotu(v9ses)) {
 		if ((mode & P9_DMSETUID) == P9_DMSETUID)
 			res |= S_ISUID;
-- 
2.43.0