[PATCH 7.0 22/42] smb: client: fix dir separator in SMB1 UNIX mounts

Greg Kroah-Hartman
2026-04-24T13:32:34Z

From: Paulo Alcantara <pc@manguebit.org>

commit c4d3fc5844d685441befd0caaab648321013cdfd upstream.

When calling cifs_mount_get_tcon() with SMB1 UNIX mounts,
@cifs_sb->mnt_cifs_flags needs to be read or updated only after
calling reset_cifs_unix_caps(), otherwise it might end up with missing
CIFS_MOUNT_POSIXACL and CIFS_MOUNT_POSIX_PATHS bits.

This fixes the wrong dir separator used in paths caused by the missing
CIFS_MOUNT_POSIX_PATHS bit in cifs_sb_info::mnt_cifs_flags.

Reported-by: "Kris Karas (Bug Reporting)" <bugs-a21@moonlit-rail.com>
Closes: https://lore.kernel.org/r/f758f4ff-4d54-4244-931d-38f469c3ff14@moonlit-rail.com
Fixes: 4fc3a433c139 ("smb: client: use atomic_t for mnt_cifs_flags")
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Cc: David Howells <dhowells@redhat.com>
Cc: linux-cifs@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/smb/client/connect.c | 10 +++++-----
fs/smb/client/smb1ops.c | 19 ++++++++-----------
2 files changed, 13 insertions(+), 16 deletions(-)

--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -3610,7 +3610,6 @@ int cifs_mount_get_tcon(struct cifs_moun
server = mnt_ctx->server;
ctx = mnt_ctx->fs_ctx;
cifs_sb = mnt_ctx->cifs_sb;
- sbflags = cifs_sb_flags(cifs_sb);

/* search for existing tcon to this server share */
tcon = cifs_get_tcon(mnt_ctx->ses, ctx);
@@ -3625,9 +3624,10 @@ int cifs_mount_get_tcon(struct cifs_moun
* path (i.e., do not remap / and \ and do not map any special characters)
*/
if (tcon->posix_extensions) {
- sbflags |= CIFS_MOUNT_POSIX_PATHS;
- sbflags &= ~(CIFS_MOUNT_MAP_SFM_CHR |
- CIFS_MOUNT_MAP_SPECIAL_CHR);
+ atomic_or(CIFS_MOUNT_POSIX_PATHS, &cifs_sb->mnt_cifs_flags);
+ atomic_andnot(CIFS_MOUNT_MAP_SFM_CHR |
+ CIFS_MOUNT_MAP_SPECIAL_CHR,
+ &cifs_sb->mnt_cifs_flags);
}

#ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
@@ -3651,6 +3651,7 @@ int cifs_mount_get_tcon(struct cifs_moun
#endif /* CONFIG_CIFS_ALLOW_INSECURE_LEGACY */
tcon->unix_ext = 0; /* server does not support them */

+ sbflags = cifs_sb_flags(cifs_sb);
/* do not care if a following call succeed - informational */
if (!tcon->pipe && server->ops->qfs_tcon) {
server->ops->qfs_tcon(mnt_ctx->xid, tcon, cifs_sb);
@@ -3675,7 +3676,6 @@ int cifs_mount_get_tcon(struct cifs_moun

out:
mnt_ctx->tcon = tcon;
- atomic_set(&cifs_sb->mnt_cifs_flags, sbflags);
return rc;
}

--- a/fs/smb/client/smb1ops.c
+++ b/fs/smb/client/smb1ops.c
@@ -49,7 +49,6 @@ void reset_cifs_unix_caps(unsigned int x

if (!CIFSSMBQFSUnixInfo(xid, tcon)) {
__u64 cap = le64_to_cpu(tcon->fsUnixInfo.Capability);
- unsigned int sbflags;

cifs_dbg(FYI, "unix caps which server supports %lld\n", cap);
/*
@@ -76,29 +75,27 @@ void reset_cifs_unix_caps(unsigned int x
if (cap & CIFS_UNIX_TRANSPORT_ENCRYPTION_MANDATORY_CAP)
cifs_dbg(VFS, "per-share encryption not supported yet\n");

- if (cifs_sb)
- sbflags = cifs_sb_flags(cifs_sb);
-
cap &= CIFS_UNIX_CAP_MASK;
if (ctx && ctx->no_psx_acl)
cap &= ~CIFS_UNIX_POSIX_ACL_CAP;
else if (CIFS_UNIX_POSIX_ACL_CAP & cap) {
cifs_dbg(FYI, "negotiated posix acl support\n");
- if (cifs_sb)
- sbflags |= CIFS_MOUNT_POSIXACL;
+ if (cifs_sb) {
+ atomic_or(CIFS_MOUNT_POSIXACL,
+ &cifs_sb->mnt_cifs_flags);
+ }
}

if (ctx && ctx->posix_paths == 0)
cap &= ~CIFS_UNIX_POSIX_PATHNAMES_CAP;
else if (cap & CIFS_UNIX_POSIX_PATHNAMES_CAP) {
cifs_dbg(FYI, "negotiate posix pathnames\n");
- if (cifs_sb)
- sbflags |= CIFS_MOUNT_POSIX_PATHS;
+ if (cifs_sb) {
+ atomic_or(CIFS_MOUNT_POSIX_PATHS,
+ &cifs_sb->mnt_cifs_flags);
+ }
}

- if (cifs_sb)
- atomic_set(&cifs_sb->mnt_cifs_flags, sbflags);
-
cifs_dbg(FYI, "Negotiate caps 0x%x\n", (int)cap);
#ifdef CONFIG_CIFS_DEBUG2
if (cap & CIFS_UNIX_FCNTL_CAP)