6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paulo Alcantara <pc@xxxxxxxxxxxxx>
commit e6322fd177c6885a21dd4609dc5e5c973d1a2eb7 upstream.
All release_mid() callers seem to hold a reference of @mid so there is
no need to call kref_put(&mid->refcount, __release_mid) under
@server->mid_lock spinlock. If they don't, then an use-after-free bug
would have occurred anyways.
By getting rid of such spinlock also fixes a potential deadlock as
shown below
CPU 0 CPU 1
------------------------------------------------------------------
cifs_demultiplex_thread() cifs_debug_data_proc_show()
release_mid()
spin_lock(&server->mid_lock);
spin_lock(&cifs_tcp_ses_lock)
spin_lock(&server->mid_lock)
__release_mid()
smb2_find_smb_tcon()
spin_lock(&cifs_tcp_ses_lock) *deadlock*
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/smb/client/cifsproto.h | 7 ++++++-
fs/smb/client/smb2misc.c | 2 +-
fs/smb/client/transport.c | 11 +----------
3 files changed, 8 insertions(+), 12 deletions(-)
--- a/fs/smb/client/cifsproto.h
+++ b/fs/smb/client/cifsproto.h
@@ -79,7 +79,7 @@ extern char *cifs_compose_mount_options(
const char *fullpath, const struct dfs_info3_param *ref,
char **devname);
extern void delete_mid(struct mid_q_entry *mid);
-extern void release_mid(struct mid_q_entry *mid);
+void __release_mid(struct kref *refcount);
extern void cifs_wake_up_task(struct mid_q_entry *mid);
extern int cifs_handle_standard(struct TCP_Server_Info *server,
struct mid_q_entry *mid);
@@ -694,4 +694,9 @@ struct super_block *cifs_get_tcon_super(
void cifs_put_tcon_super(struct super_block *sb);
int cifs_wait_for_server_reconnect(struct TCP_Server_Info *server, bool retry);
+static inline void release_mid(struct mid_q_entry *mid)
+{
+ kref_put(&mid->refcount, __release_mid);
+}
+
#endif /* _CIFSPROTO_H */
--- a/fs/smb/client/smb2misc.c
+++ b/fs/smb/client/smb2misc.c
@@ -787,7 +787,7 @@ __smb2_handle_cancelled_cmd(struct cifs_
{
struct close_cancelled_open *cancelled;
- cancelled = kzalloc(sizeof(*cancelled), GFP_ATOMIC);
+ cancelled = kzalloc(sizeof(*cancelled), GFP_KERNEL);
if (!cancelled)
return -ENOMEM;
--- a/fs/smb/client/transport.c
+++ b/fs/smb/client/transport.c
@@ -76,7 +76,7 @@ alloc_mid(const struct smb_hdr *smb_buff
return temp;
}
-static void __release_mid(struct kref *refcount)
+void __release_mid(struct kref *refcount)
{
struct mid_q_entry *midEntry =
container_of(refcount, struct mid_q_entry, refcount);
@@ -156,15 +156,6 @@ static void __release_mid(struct kref *r
mempool_free(midEntry, cifs_mid_poolp);
}
-void release_mid(struct mid_q_entry *mid)
-{
- struct TCP_Server_Info *server = mid->server;
-
- spin_lock(&server->mid_lock);
- kref_put(&mid->refcount, __release_mid);
- spin_unlock(&server->mid_lock);
-}
-
void
delete_mid(struct mid_q_entry *mid)
{
