[PATCH AUTOSEL for 4.9 056/156] afs: Adjust mode bits processing

[alexander . levin]

From: Marc Dionne <marc.dionne@xxxxxxxxxxxx>

[ Upstream commit 627f46943ff90bcc32ddeb675d881c043c6fa2ae ]

Mode bits for an afs file should not be enforced in the usual
way.

For files, the absence of user bits can restrict file access
with respect to what is granted by the server.

These bits apply regardless of the owner or the current uid; the
rest of the mode bits (group, other) are ignored.

Signed-off-by: Marc Dionne <marc.dionne@xxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 fs/afs/security.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/afs/security.c b/fs/afs/security.c
index 8d010422dc89..bfa9d3428383 100644
--- a/fs/afs/security.c
+++ b/fs/afs/security.c
@@ -340,17 +340,22 @@ int afs_permission(struct inode *inode, int mask)
 	} else {
 		if (!(access & AFS_ACE_LOOKUP))
 			goto permission_denied;
+		if ((mask & MAY_EXEC) && !(inode->i_mode & S_IXUSR))
+			goto permission_denied;
 		if (mask & (MAY_EXEC | MAY_READ)) {
 			if (!(access & AFS_ACE_READ))
 				goto permission_denied;
+			if (!(inode->i_mode & S_IRUSR))
+				goto permission_denied;
 		} else if (mask & MAY_WRITE) {
 			if (!(access & AFS_ACE_WRITE))
 				goto permission_denied;
+			if (!(inode->i_mode & S_IWUSR))
+				goto permission_denied;
 		}
 	}
 
 	key_put(key);
-	ret = generic_permission(inode, mask);
 	_leave(" = %d", ret);
 	return ret;
 
-- 
2.11.0