[PATCH v3 1/7] smb: client: fix uid/gid override in getattr with posix extensions

[Paulo Alcantara <pc@manguebit.org>]

When mounting with 'multiuser,posix' options, cifs_getattr() overrides
the server-provided uid/gid with the current process's fsuid/fsgid.
This is because the condition only checks for unix extensions
(tcon->unix_ext) but not posix extensions (tcon->posix_extensions).

With SMB3 POSIX extensions, the server provides real uid/gid values
just like with unix extensions, so they should be preserved rather
than replaced with the caller's credentials.

Add a tcon->posix_extensions check to the condition so that uid/gid
from the server are properly reported in stat results.

Reported-by: Arthur Lesuisse <arthur.lesuisse@ulb.be>
Closes: https://lore.kernel.org/r/DB9P190MB2012266F6B8DECBE5D26A1798DB52@DB9P190MB2012.EURP190.PROD.OUTLOOK.COM
Suggested-by: Arthur Lesuisse <arthur.lesuisse@ulb.be>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/inode.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c
index 12ed8db10e00..49f9993ad567 100644
--- a/fs/smb/client/inode.c
+++ b/fs/smb/client/inode.c
@@ -2992,14 +2992,14 @@ int cifs_getattr(struct mnt_idmap *idmap, const struct path *path,
 		stat->attributes |= STATX_ATTR_ENCRYPTED;
 
 	/*
-	 * If on a multiuser mount without unix extensions or cifsacl being
-	 * enabled, and the admin hasn't overridden them, set the ownership
-	 * to the fsuid/fsgid of the current process.
+	 * If on a multiuser mount without unix extensions, posix extensions
+	 * or cifsacl being enabled, and the admin hasn't overridden them,
+	 * set the ownership to the fsuid/fsgid of the current process.
 	 */
 	sbflags = cifs_sb_flags(cifs_sb);
 	if ((sbflags & CIFS_MOUNT_MULTIUSER) &&
 	    !(sbflags & CIFS_MOUNT_CIFS_ACL) &&
-	    !tcon->unix_ext) {
+	    !tcon->unix_ext && !tcon->posix_extensions) {
 		if (!(sbflags & CIFS_MOUNT_OVERR_UID))
 			stat->uid = current_fsuid();
 		if (!(sbflags & CIFS_MOUNT_OVERR_GID))
-- 
2.55.0