From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Paulo Alcantara <pc@manguebit.org>,
	Namjae Jeon <linkinjeon@kernel.org>,
	Ronnie Sahlberg <ronniesahlberg@gmail.com>,
	Shyam Prasad N <sprasad@microsoft.com>,
	Tom Talpey <tom@talpey.com>,
	Bharath SM <bharathsm@microsoft.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18.y 1/3] smb: client: fix WSL reparse point uid/gid override
Date: Tue, 22 Sep 2026 15:48:10 -0400
Message-ID: <20260922194812.85938-1-sashal@kernel.org>
In-Reply-To: <2026092249-multitude-amigo-b729@gregkh>
References: <2026092249-multitude-amigo-b729@gregkh>
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MIME-Version: 1.0
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From: Paulo Alcantara <pc@manguebit.org>

[ Upstream commit cd2b2b57921d4caa7875e83198bb2aa71254328b ]

wsl_to_fattr() unconditionally overwrites cf_uid/cf_gid with values
from WSL extended attributes ($LXUID/$LXGID), ignoring the forceuid
and forcegid mount options.

Fix this by initializing cf_uid/cf_gid to the mount defaults and
gating the $LXUID/$LXGID EA parsing on forceuid/forcegid.

Closes: https://sashiko.dev/#/patchset/20260906190803.667489-1-pc%40manguebit.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.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

Backport adaptation for Linux 6.18:
Keep the existing S_IFMT clearing from 99daf7535445 when adding the
mount-default UID/GID initialization.  The stable branch already has
that file-type fix, which followed this dependency upstream.

Also include the two wsl_to_fattr() mode-read conversions from
e1aeaf79dea5 and include linux/unaligned.h directly.  These are the
remaining context changes needed for e1253a82bb4c to apply unchanged;
the other helper conversions are outside this target's context.

Stable-dep-of: e1253a82bb4c ("smb: client: fix fattr leaking on wsl_to_fattr() failure")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/smb/client/reparse.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 6ec6b8c46ba22..c87b282da1ce9 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -6,6 +6,7 @@
 #include <linux/fs.h>
 #include <linux/stat.h>
 #include <linux/slab.h>
+#include <linux/unaligned.h>
 #include "cifsglob.h"
 #include "smb2proto.h"
 #include "cifsproto.h"
@@ -1109,10 +1110,14 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
 			 struct cifs_sb_info *cifs_sb,
 			 u32 tag, struct cifs_fattr *fattr)
 {
+	unsigned int sbflags = cifs_sb_flags(cifs_sb);
 	struct smb2_file_full_ea_info *ea;
 	bool have_xattr_dev = false;
 	u32 next = 0;
 
+	fattr->cf_uid = cifs_sb->ctx->linux_uid;
+	fattr->cf_gid = cifs_sb->ctx->linux_gid;
+
 	fattr->cf_mode &= ~S_IFMT;
 	switch (tag) {
 	case IO_REPARSE_TAG_LX_SYMLINK:
@@ -1150,15 +1155,17 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
 		nlen = ea->ea_name_length;
 		v = (void *)((u8 *)ea->ea_data + ea->ea_name_length + 1);
 
-		if (!strncmp(name, SMB2_WSL_XATTR_UID, nlen))
-			fattr->cf_uid = wsl_make_kuid(cifs_sb, v);
-		else if (!strncmp(name, SMB2_WSL_XATTR_GID, nlen))
-			fattr->cf_gid = wsl_make_kgid(cifs_sb, v);
-		else if (!strncmp(name, SMB2_WSL_XATTR_MODE, nlen)) {
+		if (!strncmp(name, SMB2_WSL_XATTR_UID, nlen)) {
+			if (!(sbflags & CIFS_MOUNT_OVERR_UID))
+				fattr->cf_uid = wsl_make_kuid(cifs_sb, v);
+		} else if (!strncmp(name, SMB2_WSL_XATTR_GID, nlen)) {
+			if (!(sbflags & CIFS_MOUNT_OVERR_GID))
+				fattr->cf_gid = wsl_make_kgid(cifs_sb, v);
+		} else if (!strncmp(name, SMB2_WSL_XATTR_MODE, nlen)) {
 			/* File type in reparse point tag and in xattr mode must match. */
-			if (S_DT(fattr->cf_mode) != S_DT(le32_to_cpu(*(__le32 *)v)))
+			if (S_DT(fattr->cf_mode) != S_DT(get_unaligned_le32(v)))
 				return false;
-			fattr->cf_mode = (umode_t)le32_to_cpu(*(__le32 *)v);
+			fattr->cf_mode = (umode_t)get_unaligned_le32(v);
 		} else if (!strncmp(name, SMB2_WSL_XATTR_DEV, nlen)) {
 			fattr->cf_rdev = reparse_mkdev(v);
 			have_xattr_dev = true;
-- 
2.53.0