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| author | Rabin Vincent <rabin.vincent@axis.com> | 2015-12-23 07:32:41 +0100 |
|---|---|---|
| committer | Steve French <sfrench@localhost.localdomain> | 2016-01-14 14:35:58 -0600 |
| commit | 820962dc700598ffe8cd21b967e30e7520c34748 (patch) | |
| tree | 21cfcb56a523a372e1518d7fce1ed9e7cccb0df5 /fs/cifs/connect.c | |
| parent | 373512ec5c105ed09e3738196dcb257dfab65cba (diff) | |
| download | linux-820962dc700598ffe8cd21b967e30e7520c34748.tar.bz2 | |
cifs: fix race between call_async() and reconnect()
cifs_call_async() queues the MID to the pending list and calls
smb_send_rqst(). If smb_send_rqst() performs a partial send, it sets
the tcpStatus to CifsNeedReconnect and returns an error code to
cifs_call_async(). In this case, cifs_call_async() removes the MID
from the list and returns to the caller.
However, cifs_call_async() releases the server mutex _before_ removing
the MID. This means that a cifs_reconnect() can race with this function
and manage to remove the MID from the list and delete the entry before
cifs_call_async() calls cifs_delete_mid(). This leads to various
crashes due to the use after free in cifs_delete_mid().
Task1 Task2
cifs_call_async():
- rc = -EAGAIN
- mutex_unlock(srv_mutex)
cifs_reconnect():
- mutex_lock(srv_mutex)
- mutex_unlock(srv_mutex)
- list_delete(mid)
- mid->callback()
cifs_writev_callback():
- mutex_lock(srv_mutex)
- delete(mid)
- mutex_unlock(srv_mutex)
- cifs_delete_mid(mid) <---- use after free
Fix this by removing the MID in cifs_call_async() before releasing the
srv_mutex. Also hold the srv_mutex in cifs_reconnect() until the MIDs
are moved out of the pending list.
Signed-off-by: Rabin Vincent <rabin.vincent@axis.com>
Acked-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <sfrench@localhost.localdomain>
Diffstat (limited to 'fs/cifs/connect.c')
| -rw-r--r-- | fs/cifs/connect.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 6ab9e83b899e..4fbd92d2e113 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -370,7 +370,6 @@ cifs_reconnect(struct TCP_Server_Info *server) server->session_key.response = NULL; server->session_key.len = 0; server->lstrp = jiffies; - mutex_unlock(&server->srv_mutex); /* mark submitted MIDs for retry and issue callback */ INIT_LIST_HEAD(&retry_list); @@ -383,6 +382,7 @@ cifs_reconnect(struct TCP_Server_Info *server) list_move(&mid_entry->qhead, &retry_list); } spin_unlock(&GlobalMid_Lock); + mutex_unlock(&server->srv_mutex); cifs_dbg(FYI, "%s: issuing mid callbacks\n", __func__); list_for_each_safe(tmp, tmp2, &retry_list) { |