at 02:28, Pavel Shilovsky <piastryyy@xxxxxxxxx> wrote:
вт, 7 мая 2019 г. в 09:13, Steve French via samba-technical
<samba-technical@xxxxxxxxxxxxxxx>:
merged into cifs-2.6.git for-next
On Tue, May 7, 2019 at 10:17 AM Christoph Probst via samba-technical
<samba-technical@xxxxxxxxxxxxxxx> wrote:
Change strcat to strncpy in the "None" case to fix a buffer overflow
when cinode->oplock is reset to 0 by another thread accessing the same
cinode. It is never valid to append "None" to any other message.
Consolidate multiple writes to cinode->oplock to reduce raciness.
Signed-off-by: Christoph Probst <kernel@xxxxxxxxx>
---
fs/cifs/smb2ops.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index c36ff0d..aa61dcf 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -2917,26 +2917,28 @@ smb21_set_oplock_level(struct cifsInodeInfo
*cinode, __u32 oplock,
unsigned int epoch, bool *purge_cache)
{
char message[5] = {0};
+ unsigned int new_oplock = 0;
oplock &= 0xFF;
if (oplock == SMB2_OPLOCK_LEVEL_NOCHANGE)
return;
- cinode->oplock = 0;
if (oplock & SMB2_LEASE_READ_CACHING_HE) {
- cinode->oplock |= CIFS_CACHE_READ_FLG;
+ new_oplock |= CIFS_CACHE_READ_FLG;
strcat(message, "R");
}
if (oplock & SMB2_LEASE_HANDLE_CACHING_HE) {
- cinode->oplock |= CIFS_CACHE_HANDLE_FLG;
+ new_oplock |= CIFS_CACHE_HANDLE_FLG;
strcat(message, "H");
}
if (oplock & SMB2_LEASE_WRITE_CACHING_HE) {
- cinode->oplock |= CIFS_CACHE_WRITE_FLG;
+ new_oplock |= CIFS_CACHE_WRITE_FLG;
strcat(message, "W");
}
- if (!cinode->oplock)
- strcat(message, "None");
+ if (!new_oplock)
+ strncpy(message, "None", sizeof(message));
+
+ cinode->oplock = new_oplock;
cifs_dbg(FYI, "%s Lease granted on inode %p\n", message,
&cinode->vfs_inode);
}
--
2.1.4
Doesn’t the race still happen, but implicitly here?
cinode->oplock = new_oplock;
Is it possible to just introduce a lock to force its proper ordering?
e.g.
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index bf5b8264e119..a3c3c6156d17 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -267,6 +267,7 @@ cifs_alloc_inode(struct super_block *sb)
* server, can not assume caching of file data or metadata.
*/
cifs_set_oplock_level(cifs_inode, 0);
+ mutex_init(&cifs_inode->oplock_mutex);
cifs_inode->flags = 0;
spin_lock_init(&cifs_inode->writers_lock);
cifs_inode->writers = 0;
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 37b5ddf27ff1..6dfd4ab16c4f 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1214,6 +1214,7 @@ struct cifsInodeInfo {
struct list_head openFileList;
__u32 cifsAttrs; /* e.g. DOS archive bit, sparse, compressed, system */
unsigned int oplock; /* oplock/lease level we have */
+ struct mutex oplock_mutex;
unsigned int epoch; /* used to track lease state changes */
#define CIFS_INODE_PENDING_OPLOCK_BREAK (0) /* oplock break in progress */
#define CIFS_INODE_PENDING_WRITERS (1) /* Writes in progress */
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index b20063cf774f..796b23712e71 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -1901,6 +1901,7 @@ smb21_set_oplock_level(struct cifsInodeInfo *cinode,
__u32 oplock,
if (oplock == SMB2_OPLOCK_LEVEL_NOCHANGE)
return;
+ mutex_lock(&cinode->oplock_mutex);
cinode->oplock = 0;
if (oplock & SMB2_LEASE_READ_CACHING_HE) {
cinode->oplock |= CIFS_CACHE_READ_FLG;
@@ -1916,6 +1917,8 @@ smb21_set_oplock_level(struct cifsInodeInfo *cinode,
__u32 oplock,
}
if (!cinode->oplock)
strcat(message, "None");
+ mutex_unlock(&cinode->oplock_mutex);
+
cifs_dbg(FYI, "%s Lease granted on inode %p\n", message,
&cinode->vfs_inode);
}
Kai-Heng
Thanks for cleaning it up!
Reviewed-by: Pavel Shilovsky <pshilov@xxxxxxxxxxxxx>
--
Best regards,
Pavel Shilovsky
