i4l: fix random freezes with AVM B1 drivers

This fix the same issue which was debbuged for the C4 controller for the B1
versions.

The capilib_ function modify or traverse a linked list without locking.

This patch extends the existing locking to the calls of these function to
prevent access to a list which is in the middle of a modification.

Signed-off-by: Karsten Keil <kkeil@suse.de>
C: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 15 deletions

diff --git a/drivers/isdn/hardware/avm/b1.c b/drivers/isdn/hardware/avm/b1.c
index 7a69a18d07e2..4484a6417235 100644
--- a/drivers/isdn/hardware/avm/b1.c
+++ b/drivers/isdn/hardware/avm/b1.c
@@ -321,12 +321,15 @@ void b1_reset_ctr(struct capi_ctr *ctrl)
         avmctrl_info *cinfo = (avmctrl_info *)(ctrl->driverdata);
         avmcard *card = cinfo->card;
         unsigned int port = card->port;
+        unsigned long flags;
 
         b1_reset(port);
         b1_reset(port);
 
         memset(cinfo->version, 0, sizeof(cinfo->version));
+        spin_lock_irqsave(&card->lock, flags);
         capilib_release(&cinfo->ncci_head);
+        spin_unlock_irqrestore(&card->lock, flags);
         capi_ctr_reseted(ctrl);
 }
 
@@ -361,9 +364,8 @@ void b1_release_appl(struct capi_ctr *ctrl, u16 appl)
         unsigned int port = card->port;
         unsigned long flags;
 
-        capilib_release_appl(&cinfo->ncci_head, appl);
-
         spin_lock_irqsave(&card->lock, flags);
+        capilib_release_appl(&cinfo->ncci_head, appl);
         b1_put_byte(port, SEND_RELEASE);
         b1_put_word(port, appl);
         spin_unlock_irqrestore(&card->lock, flags);
@@ -380,27 +382,27 @@ u16 b1_send_message(struct capi_ctr *ctrl, struct sk_buff *skb)
         u8 subcmd = CAPIMSG_SUBCOMMAND(skb->data);
         u16 dlen, retval;
 
+        spin_lock_irqsave(&card->lock, flags);
         if (CAPICMD(cmd, subcmd) == CAPI_DATA_B3_REQ) {
                 retval = capilib_data_b3_req(&cinfo->ncci_head,
                                              CAPIMSG_APPID(skb->data),
                                              CAPIMSG_NCCI(skb->data),
                                              CAPIMSG_MSGID(skb->data));
-                if (retval != CAPI_NOERROR) 
+                if (retval != CAPI_NOERROR) {
+                        spin_unlock_irqrestore(&card->lock, flags);
                         return retval;
+                }
 
                 dlen = CAPIMSG_DATALEN(skb->data);
 
-                spin_lock_irqsave(&card->lock, flags);
                 b1_put_byte(port, SEND_DATA_B3_REQ);
                 b1_put_slice(port, skb->data, len);
                 b1_put_slice(port, skb->data + len, dlen);
-                spin_unlock_irqrestore(&card->lock, flags);
         } else {
-                spin_lock_irqsave(&card->lock, flags);
                 b1_put_byte(port, SEND_MESSAGE);
                 b1_put_slice(port, skb->data, len);
-                spin_unlock_irqrestore(&card->lock, flags);
         }
+        spin_unlock_irqrestore(&card->lock, flags);
 
         dev_kfree_skb_any(skb);
         return CAPI_NOERROR;
@@ -534,17 +536,17 @@ irqreturn_t b1_interrupt(int interrupt, void *devptr)
 
                 ApplId = (unsigned) b1_get_word(card->port);
                 MsgLen = b1_get_slice(card->port, card->msgbuf);
-                spin_unlock_irqrestore(&card->lock, flags);
                 if (!(skb = alloc_skb(MsgLen, GFP_ATOMIC))) {
                         printk(KERN_ERR "%s: incoming packet dropped\n",
                                         card->name);
+                        spin_unlock_irqrestore(&card->lock, flags);
                 } else {
                         memcpy(skb_put(skb, MsgLen), card->msgbuf, MsgLen);
                         if (CAPIMSG_CMD(skb->data) == CAPI_DATA_B3_CONF)
                                 capilib_data_b3_conf(&cinfo->ncci_head, ApplId,
                                                      CAPIMSG_NCCI(skb->data),
                                                      CAPIMSG_MSGID(skb->data));
-
+                        spin_unlock_irqrestore(&card->lock, flags);
                         capi_ctr_handle_message(ctrl, ApplId, skb);
                 }
                 break;
@@ -554,21 +556,17 @@ irqreturn_t b1_interrupt(int interrupt, void *devptr)
                 ApplId = b1_get_word(card->port);
                 NCCI = b1_get_word(card->port);
                 WindowSize = b1_get_word(card->port);
-                spin_unlock_irqrestore(&card->lock, flags);
-
                 capilib_new_ncci(&cinfo->ncci_head, ApplId, NCCI, WindowSize);
-
+                spin_unlock_irqrestore(&card->lock, flags);
                 break;
 
         case RECEIVE_FREE_NCCI:
 
                 ApplId = b1_get_word(card->port);
                 NCCI = b1_get_word(card->port);
-                spin_unlock_irqrestore(&card->lock, flags);
-
                 if (NCCI != 0xffffffff)
                         capilib_free_ncci(&cinfo->ncci_head, ApplId, NCCI);
-               
+                spin_unlock_irqrestore(&card->lock, flags);
                 break;
 
         case RECEIVE_START: