[PATCH 5.15.y] smb: client: fix atomic open with O_DIRECT & O_SYNC

Sasha Levin
2026-03-19T16:44:51Z

From: Paulo Alcantara <pc@manguebit.org>

[ Upstream commit 4a7d2729dc99437dbb880a64c47828c0d191b308 ]

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>
[ adapted file paths from fs/smb/client/ to fs/cifs/ ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/cifs/cifsglob.h | 11 +++++++++++
fs/cifs/dir.c | 1 +
fs/cifs/file.c | 17 +++--------------
3 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 68b9b382d44bf..7d044ce518f61 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -17,6 +17,7 @@
#include <linux/mm.h>
#include <linux/mempool.h>
#include <linux/workqueue.h>
+#include <linux/fcntl.h>
#include "cifs_fs_sb.h"
#include "cifsacl.h"
#include <crypto/internal/hash.h>
@@ -2050,4 +2051,14 @@ static inline bool cifs_ses_exiting(struct cifs_ses *ses)
return ret;
}

+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 */
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 83c929dd6ed59..7cb7db5c44128 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -293,6 +293,7 @@ cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned int xid,
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
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 10bb1f9551887..0068c46cd0735 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -205,19 +205,13 @@ cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_sb_info *ci
*********************************************************************/

disposition = cifs_get_disposition(f_flags);
-
/* BB pass O_SYNC flag through on file attributes .. BB */

buf = kmalloc(sizeof(FILE_ALL_INFO), GFP_KERNEL);
if (!buf)
return -ENOMEM;

- /* 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);

oparms.tcon = tcon;
oparms.cifs_sb = cifs_sb;
@@ -770,13 +764,8 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
}

desired_access = cifs_convert_flags(cfile->f_flags);
-
- /* 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);
--
2.51.0