[PATCH 6.6.y 2/3] smb: client: use atomic_t for mnt_cifs_flags

[Sasha Levin <sashal@kernel.org>]

From: Paulo Alcantara <pc@manguebit.org>

[ Upstream commit 4fc3a433c13944ee5766ec5b9bf6f1eb4d29b880 ]

Use atomic_t for cifs_sb_info::mnt_cifs_flags as it's currently
accessed locklessly and may be changed concurrently in mount/remount
and reconnect paths.

Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Cc: linux-cifs@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>

[ Stable dependency adaptation for cd2b2b57921d:
  The 6.6 WSL parser already matches the target's preimage. Keep only the
  cifs_sb_flags interface needed by that fix and its WSL uid/gid callers.
  Implement the accessor as a READ_ONCE macro over the existing unsigned
  mount flags, without adding functions. Drop the atomic_t conversion,
  generic CIFS_SB accessors and unrelated client-wide refactoring, which
  depend on newer SMB code absent from this tree. This is preparation for
  the WSL ownership fix, not a backport of the full flag-writer race fix. ]

[ sashal: Reduced backport -- upstream 4fc3a433c1394 touches 27 file(s), this
  backport carries 2. Not backported here:
  fs/smb/client/cached_dir.c
  fs/smb/client/cifsacl.c
  fs/smb/client/cifsfs.c
  fs/smb/client/cifs_fs_sb.h
  fs/smb/client/cifs_ioctl.h
  fs/smb/client/cifs_unicode.c
  fs/smb/client/cifs_unicode.h
  fs/smb/client/connect.c
  ... and 17 more
  This note is generated from the file lists only; see the resolution record
  for the reasoning. ]

Stable-dep-of: cd2b2b57921d ("smb: client: fix WSL reparse point uid/gid override")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/smb/client/cifsglob.h | 3 +++
 fs/smb/client/reparse.h  | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index a4e0618c58efc..61ebd6d8eb41e 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1603,6 +1603,9 @@ CIFS_FILE_SB(struct file *file)
 	return CIFS_SB(file_inode(file)->i_sb);
 }
 
+/* Read mount flags once for paths that need a consistent snapshot. */
+#define cifs_sb_flags(cifs_sb) READ_ONCE((cifs_sb)->mnt_cifs_flags)
+
 static inline char CIFS_DIR_SEP(const struct cifs_sb_info *cifs_sb)
 {
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS)
diff --git a/fs/smb/client/reparse.h b/fs/smb/client/reparse.h
index ff05b0e75c928..c15e4541cca06 100644
--- a/fs/smb/client/reparse.h
+++ b/fs/smb/client/reparse.h
@@ -32,7 +32,7 @@ static inline kuid_t wsl_make_kuid(struct cifs_sb_info *cifs_sb,
 {
 	u32 uid = le32_to_cpu(*(__le32 *)ptr);
 
-	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_OVERR_UID)
+	if (cifs_sb_flags(cifs_sb) & CIFS_MOUNT_OVERR_UID)
 		return cifs_sb->ctx->linux_uid;
 	return make_kuid(current_user_ns(), uid);
 }
@@ -42,7 +42,7 @@ static inline kgid_t wsl_make_kgid(struct cifs_sb_info *cifs_sb,
 {
 	u32 gid = le32_to_cpu(*(__le32 *)ptr);
 
-	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_OVERR_GID)
+	if (cifs_sb_flags(cifs_sb) & CIFS_MOUNT_OVERR_GID)
 		return cifs_sb->ctx->linux_gid;
 	return make_kgid(current_user_ns(), gid);
 }
-- 
2.53.0