Re: kernel BUG at net/core/skbuff.c in linux-2.6.21-rc6

Patrick McHardy
2007-04-12T05:44:08Z

[-- Attachment #1: Type: text/plain, Size: 1193 bytes --]

Bartek wrote:
> Hopefully, this time it my bug report should be ok :):
>
> Apr 11 23:53:38 localhost pppd[31289]: rcvd [proto=0x7689] e1 cd 33 f6
> fd f7 52 e6 58 c9 73 98 bc ff ad d5 b5 a3 e5 d9 1e 77 76 0a 1c 87 59
> bf 44 cc ac 3b ...
> Apr 11 23:53:38 localhost pppd[31289]: Unsupported protocol 0x7689 received
> Apr 11 23:53:38 localhost pppd[31289]: sent [LCP ProtRej id=0x9 76 89
> e1 cd 33 f6 fd f7 52 e6 58 c9 73 98 bc ff ad d5 b5 a3 e5 d9 1e 77 76
> 0a 1c 87 59 bf 44 cc ...]
> Apr 11 23:53:38 localhost pppd[31289]: rcvd [proto=0xda7d] 15 19 45 3c
> e0 ac 44 92 3b c4 8e 75 6b b8 4a 9f 4a 3a 22 63 d3 a1 56 98 47 62 bc
> cd a6 8e d5 77 ...
> Apr 11 23:53:38 localhost pppd[31289]: Unsupported protocol 0xda7d received
> Apr 11 23:53:38 localhost pppd[31289]: sent [LCP ProtRej id=0xa da 7d
> 15 19 45 3c e0 ac 44 92 3b c4 8e 75 6b b8 4a 9f 4a 3a 22 63 d3 a1 56
> 98 47 62 bc cd a6 8e ...]
> Apr 11 23:53:40 localhost kernel: skb_under_panic: text:f8c62c0e
> len:291 put:1 head:ddc94800 data:ddc947ff tail:ddc94922 end:ddc94e00
> dev:<NULL>

It seems we fail to reserve enough headroom for the case
buf[0] == PPP_ALLSTATIONS and buf[1] != PPP_UI.

Can you try this patch please?

[-- Attachment #2: x --]
[-- Type: text/plain, Size: 841 bytes --]

diff --git a/drivers/net/ppp_async.c b/drivers/net/ppp_async.c
index 933e2f3..c68e37f 100644
--- a/drivers/net/ppp_async.c
+++ b/drivers/net/ppp_async.c
@@ -890,6 +890,8 @@ ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
ap->rpkt = skb;
}
if (skb->len == 0) {
+ int headroom = 0;
+
/* Try to get the payload 4-byte aligned.
* This should match the
* PPP_ALLSTATIONS/PPP_UI/compressed tests in
@@ -897,7 +899,10 @@ ppp_async_input(struct asyncppp *ap, const unsigned char *buf,
* enough chars here to test buf[1] and buf[2].
*/
if (buf[0] != PPP_ALLSTATIONS)
- skb_reserve(skb, 2 + (buf[0] & 1));
+ headroom += 2;
+ if (buf[0] & 1)
+ headroom += 1;
+ skb_reserve(skb, headroom);
}
if (n > skb_tailroom(skb)) {
/* packet overflowed MRU */