i4l: fix random freezes with AVM B1 drivers

patch 9713d9e650045f7f2afd81d58a068827be306993 in mainline.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/isdn/hardware/avm/b1.c b/drivers/isdn/hardware/avm/b1.c
index 7a69a18d07e245f4a15cc10631262a37c568d67c..4484a6417235ec3c87de9cbe36313a7b015bfac2 100644 (file)
--- 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: