6.1-stable review patch. If anyone has any objections, please let me know.
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From: Paulo Alcantara pc@manguebit.com
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@vger.kernel.org Signed-off-by: Paulo Alcantara (SUSE) pc@manguebit.com Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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) {