skbuff: skb_under_panic: text:ffffffff88771f69 len:56 put:-4
head:ffff88805f86a800 data:ffff887f5f86a850 tail:0x88 end:0x2c0 dev:pim6reg
------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:192!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 2 PID: 22968 Comm: kworker/2:11 Not tainted 6.5.0-rc3-00044-g0a8db05b571a #236
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: ipv6_addrconf addrconf_dad_work
RIP: 0010:skb_panic+0x152/0x1d0
Call Trace:
<TASK>
skb_push+0xc4/0xe0
ip6mr_cache_report+0xd69/0x19b0
reg_vif_xmit+0x406/0x690
dev_hard_start_xmit+0x17e/0x6e0
__dev_queue_xmit+0x2d6a/0x3d20
vlan_dev_hard_start_xmit+0x3ab/0x5c0
dev_hard_start_xmit+0x17e/0x6e0
__dev_queue_xmit+0x2d6a/0x3d20
neigh_connected_output+0x3ed/0x570
ip6_finish_output2+0x5b5/0x1950
ip6_finish_output+0x693/0x11c0
ip6_output+0x24b/0x880
NF_HOOK.constprop.0+0xfd/0x530
ndisc_send_skb+0x9db/0x1400
ndisc_send_rs+0x12a/0x6c0
addrconf_dad_completed+0x3c9/0xea0
addrconf_dad_work+0x849/0x1420
process_one_work+0xa22/0x16e0
worker_thread+0x679/0x10c0
ret_from_fork+0x28/0x60
ret_from_fork_asm+0x11/0x20
When setup a vlan device on dev pim6reg, DAD ns packet may sent on reg_vif_xmit().
reg_vif_xmit()
ip6mr_cache_report()
skb_push(skb, -skb_network_offset(pkt));//skb_network_offset(pkt) is 4
And skb_push declared as:
void *skb_push(struct sk_buff *skb, unsigned int len);
skb->data -= len;
//0xffff88805f86a84c - 0xfffffffc = 0xffff887f5f86a850
skb->data is set to 0xffff887f5f86a850, which is invalid mem addr, lead to skb_push() fails.
Fixes: 14fb64e1f449 ("[IPV6] MROUTE: Support PIM-SM (SSM).")
Signed-off-by: Yue Haibing <[email protected]>
---
v2: Use __skb_pull() and fix commit log.
---
net/ipv6/ip6mr.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index cc3d5ad17257..1a55d41feaa6 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1051,9 +1051,9 @@ static int ip6mr_cache_report(const struct mr_table *mrt, struct sk_buff *pkt,
int ret;
#ifdef CONFIG_IPV6_PIMSM_V2
+ int nhoff = skb_network_offset(pkt);
if (assert == MRT6MSG_WHOLEPKT || assert == MRT6MSG_WRMIFWHOLE)
- skb = skb_realloc_headroom(pkt, -skb_network_offset(pkt)
- +sizeof(*msg));
+ skb = skb_realloc_headroom(pkt, -nhoff + sizeof(*msg));
else
#endif
skb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(*msg), GFP_ATOMIC);
@@ -1073,7 +1073,7 @@ static int ip6mr_cache_report(const struct mr_table *mrt, struct sk_buff *pkt,
And all this only to mangle msg->im6_msgtype and
to set msg->im6_mbz to "mbz" :-)
*/
- skb_push(skb, -skb_network_offset(pkt));
+ __skb_pull(skb, nhoff);
skb_push(skb, sizeof(*msg));
skb_reset_transport_header(skb);
--
2.34.1
On Fri, 28 Jul 2023 20:17:03 +0800 Yue Haibing wrote:
> #ifdef CONFIG_IPV6_PIMSM_V2
> + int nhoff = skb_network_offset(pkt);
> if (assert == MRT6MSG_WHOLEPKT || assert == MRT6MSG_WRMIFWHOLE)
> - skb = skb_realloc_headroom(pkt, -skb_network_offset(pkt)
> - +sizeof(*msg));
> + skb = skb_realloc_headroom(pkt, -nhoff + sizeof(*msg));
These changes look unnecessary. You can leave this code be (as ugly as
it is)...
> else
> #endif
> skb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(*msg), GFP_ATOMIC);
> @@ -1073,7 +1073,7 @@ static int ip6mr_cache_report(const struct mr_table *mrt, struct sk_buff *pkt,
> And all this only to mangle msg->im6_msgtype and
> to set msg->im6_mbz to "mbz" :-)
> */
> - skb_push(skb, -skb_network_offset(pkt));
> + __skb_pull(skb, nhoff);
.. and just replace the push here with:
__skb_pull(skb, skb_network_offset(pkt));
--
pw-bot: cr
On 2023/8/1 11:09, Jakub Kicinski wrote:
> On Fri, 28 Jul 2023 20:17:03 +0800 Yue Haibing wrote:
>> #ifdef CONFIG_IPV6_PIMSM_V2
>> + int nhoff = skb_network_offset(pkt);
>> if (assert == MRT6MSG_WHOLEPKT || assert == MRT6MSG_WRMIFWHOLE)
>> - skb = skb_realloc_headroom(pkt, -skb_network_offset(pkt)
>> - +sizeof(*msg));
>> + skb = skb_realloc_headroom(pkt, -nhoff + sizeof(*msg));
>
> These changes look unnecessary. You can leave this code be (as ugly as
> it is)...
>
>> else
>> #endif
>> skb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(*msg), GFP_ATOMIC);
>> @@ -1073,7 +1073,7 @@ static int ip6mr_cache_report(const struct mr_table *mrt, struct sk_buff *pkt,
>> And all this only to mangle msg->im6_msgtype and
>> to set msg->im6_mbz to "mbz" :-)
>> */
>> - skb_push(skb, -skb_network_offset(pkt));
>> + __skb_pull(skb, nhoff);
>
> .. and just replace the push here with:
>
> __skb_pull(skb, skb_network_offset(pkt));
Thanks， will do this in v3.
>