[PATCH 1/2] smb: client: fix unaligned access in WSL reparse point parser

[Paulo Alcantara <pc@manguebit.org>]

When wsl_to_fattr() parses WSL extended attributes, it computes a
payload pointer from ea->ea_data + ea_name_length + 1.  Since the
smb2_file_full_ea_info struct is __packed and all WSL xattr names are
6 bytes long, the value pointer always lands at an odd byte offset,
never satisfying __le32 or __le64 alignment requirements.

The code then casts this pointer to __le32 * or __le64 * and
dereferences it directly, which may cause alignment faults on some
architectures.

Replace all such casts with get_unaligned_le32() and
get_unaligned_le64() in reparse_mkdev(), wsl_make_kuid(),
wsl_make_kgid() and wsl_to_fattr().

Closes: https://sashiko.dev/#/patchset/20260906200517.725015-1-pc%40manguebit.org
Fixes: 78e26bec4d6d ("smb: client: parse uid, gid, mode and dev from WSL reparse points")
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: stable@vger.kernel.org
---
 fs/smb/client/reparse.c | 4 ++--
 fs/smb/client/reparse.h | 7 ++++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 9e31fce7e0a5..6ac69f4d391a 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -1201,9 +1201,9 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
 				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;
diff --git a/fs/smb/client/reparse.h b/fs/smb/client/reparse.h
index 49efd85b1e94..05b2cecb4495 100644
--- a/fs/smb/client/reparse.h
+++ b/fs/smb/client/reparse.h
@@ -9,6 +9,7 @@
 #include <linux/fs.h>
 #include <linux/stat.h>
 #include <linux/uidgid.h>
+#include <linux/unaligned.h>
 #include "fs_context.h"
 #include "cifsglob.h"
 #include "../common/smbfsctl.h"
@@ -23,7 +24,7 @@
 
 static inline dev_t reparse_mkdev(void *ptr)
 {
-	u64 v = le64_to_cpu(*(__le64 *)ptr);
+	u64 v = get_unaligned_le64(ptr);
 
 	return MKDEV(v & 0xffffffff, v >> 32);
 }
@@ -31,7 +32,7 @@ static inline dev_t reparse_mkdev(void *ptr)
 static inline kuid_t wsl_make_kuid(struct cifs_sb_info *cifs_sb,
 				   void *ptr)
 {
-	u32 uid = le32_to_cpu(*(__le32 *)ptr);
+	u32 uid = get_unaligned_le32(ptr);
 
 	if (cifs_sb_flags(cifs_sb) & CIFS_MOUNT_OVERR_UID)
 		return cifs_sb->ctx->linux_uid;
@@ -41,7 +42,7 @@ static inline kuid_t wsl_make_kuid(struct cifs_sb_info *cifs_sb,
 static inline kgid_t wsl_make_kgid(struct cifs_sb_info *cifs_sb,
 				   void *ptr)
 {
-	u32 gid = le32_to_cpu(*(__le32 *)ptr);
+	u32 gid = get_unaligned_le32(ptr);
 
 	if (cifs_sb_flags(cifs_sb) & CIFS_MOUNT_OVERR_GID)
 		return cifs_sb->ctx->linux_gid;
-- 
2.55.0