[PATCH 6.18 284/333] smb: client: fix atomic open with O_DIRECT & O_SYNC

Greg Kroah-Hartman
2026-03-17T17:27:53Z

From: Paulo Alcantara <pc@manguebit.org>

commit 4a7d2729dc99437dbb880a64c47828c0d191b308 upstream.

When user application requests O_DIRECT|O_SYNC along with O_CREAT on
open(2), CREATE_NO_BUFFER and CREATE_WRITE_THROUGH bits were missed in
CREATE request when performing an atomic open, thus leading to
potentially data integrity issues.

Fix this by setting those missing bits in CREATE request when
O_DIRECT|O_SYNC has been specified in cifs_do_create().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Henrique Carvalho <henrique.carvalho@suse.com>
Cc: Tom Talpey <tom@talpey.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/cifsglob.h | 11 +++++++++++
fs/smb/client/dir.c | 1 +
fs/smb/client/file.c | 18 +++---------------
3 files changed, 15 insertions(+), 15 deletions(-)

--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -20,6 +20,7 @@
#include <linux/utsname.h>
#include <linux/sched/mm.h>
#include <linux/netfs.h>
+#include <linux/fcntl.h>
#include "cifs_fs_sb.h"
#include "cifsacl.h"
#include <crypto/internal/hash.h>
@@ -2396,4 +2397,14 @@ static inline void mid_execute_callback(
(le32_to_cpu((tcon)->fsAttrInfo.Attributes) & \
FILE_SUPPORTS_REPARSE_POINTS))

+static inline int cifs_open_create_options(unsigned int oflags, int opts)
+{
+ /* O_SYNC also has bit for O_DSYNC so following check picks up either */
+ if (oflags & O_SYNC)
+ opts |= CREATE_WRITE_THROUGH;
+ if (oflags & O_DIRECT)
+ opts |= CREATE_NO_BUFFER;
+ return opts;
+}
+
#endif /* _CIFS_GLOB_H */
--- a/fs/smb/client/dir.c
+++ b/fs/smb/client/dir.c
@@ -307,6 +307,7 @@ static int cifs_do_create(struct inode *
goto out;
}

+ create_options |= cifs_open_create_options(oflags, create_options);
/*
* if we're not using unix extensions, see if we need to set
* ATTR_READONLY on the create call
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -584,15 +584,8 @@ static int cifs_nt_open(const char *full
*********************************************************************/

disposition = cifs_get_disposition(f_flags);
-
/* BB pass O_SYNC flag through on file attributes .. BB */
-
- /* O_SYNC also has bit for O_DSYNC so following check picks up either */
- if (f_flags & O_SYNC)
- create_options |= CREATE_WRITE_THROUGH;
-
- if (f_flags & O_DIRECT)
- create_options |= CREATE_NO_BUFFER;
+ create_options |= cifs_open_create_options(f_flags, create_options);

retry_open:
oparms = (struct cifs_open_parms) {
@@ -1318,13 +1311,8 @@ cifs_reopen_file(struct cifsFileInfo *cf
rdwr_for_fscache = 1;

desired_access = cifs_convert_flags(cfile->f_flags, rdwr_for_fscache);
-
- /* O_SYNC also has bit for O_DSYNC so following check picks up either */
- if (cfile->f_flags & O_SYNC)
- create_options |= CREATE_WRITE_THROUGH;
-
- if (cfile->f_flags & O_DIRECT)
- create_options |= CREATE_NO_BUFFER;
+ create_options |= cifs_open_create_options(cfile->f_flags,
+ create_options);

if (server->ops->get_lease_key)
server->ops->get_lease_key(inode, &cfile->fid);