On Mon, Oct 2, 2017 at 10:21 AM, Mark Rutland <[email protected]> wrote: > On Mon, Oct 02, 2017 at 07:48:28AM -0700, Eric Dumazet wrote: >> Please try the following fool proof patch. >> >> This is what I had in my local tree back in August but could not >> conclude on the syzkaller bug I was working on. >> >> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c >> index >> 681e33998e03b609fdca83a83e0fc62a3fee8c39..e51d777797a927058760a1ab7af00579f7488cb5 >> 100644 >> --- a/net/ipv4/icmp.c >> +++ b/net/ipv4/icmp.c >> @@ -732,7 +732,8 @@ void icmp_send(struct sk_buff *skb_in, int type, int >> code, __be32 info) >> room = 576; >> room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen; >> room -= sizeof(struct icmphdr); >> - >> + if (room < 0) >> + goto ende; >> icmp_param.data_len = skb_in->len - icmp_param.offset; >> if (icmp_param.data_len > room) >> icmp_param.data_len = room; >> > > Unfortuantely, with this applied I still see the issue. > > Syzkaller came up with a minimized reproducer [1], which can trigger the > issue near instantly under syz-execprog. If there's anything that would > help to narrow this down, I'm more than happy to give it a go. > > Thanks, > Mark. > > [1] > https://www.kernel.org/pub/linux/kernel/people/mark/bugs/20171002-skb_clone-misaligned-atomic/syzkaller.repro
Note that I was not trying to address the misaligned stuff. Only this : ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:2626! Internal error: Oops - BUG: 0 [#1] PREEMPT SMP Modules linked in: CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.14.0-rc2-00001-gd7ad33d #115 Hardware name: linux,dummy-virt (DT) task: ffff80003a901a80 task.stack: ffff80003a908000 PC is at skb_copy_and_csum_bits+0x8dc/0xae0 net/core/skbuff.c:2626 LR is at skb_copy_and_csum_bits+0x8dc/0xae0 net/core/skbuff.c:2626
