On Thu, Sep 23, 2021 at 12:34:42PM +0300, Dan Carpenter wrote: > On Wed, Sep 22, 2021 at 05:18:29PM +0800, Xin Long wrote: > > On Tue, Sep 21, 2021 at 12:09 PM syzbot > > <syzbot+581aff2ae6b860625116@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: 98dc68f8b0c2 selftests: nci: replace unsigned int with int > > > git tree: net > > > console output: https://syzkaller.appspot.com/x/log.txt?x=11fd443d300000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=c31c0936547df9ea > > > dashboard link: https://syzkaller.appspot.com/bug?extid=581aff2ae6b860625116 > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+581aff2ae6b860625116@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN > > > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] > > > CPU: 0 PID: 11205 Comm: kworker/0:12 Not tainted 5.14.0-syzkaller #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > > Workqueue: ipv6_addrconf addrconf_dad_work > > > RIP: 0010:sctp_rcv_ootb net/sctp/input.c:705 [inline] > > by anyway, checking if skb_header_pointer() return NULL is always needed: > > @@ -702,7 +702,7 @@ static int sctp_rcv_ootb(struct sk_buff *skb) > > ch = skb_header_pointer(skb, offset, sizeof(*ch), &_ch); > > > > /* Break out if chunk length is less then minimal. */ > > - if (ntohs(ch->length) < sizeof(_ch)) > > + if (!ch || ntohs(ch->length) < sizeof(_ch)) > > break; > > > > The skb_header_pointer() function is annotated as __must_check but that > only means you have to use the return value. These things would be > better as a Coccinelle or Smatch check. > > I will create a Smatch warning for this. These are the Smatch warnings for this: net/sctp/input.c:705 sctp_rcv_ootb() error: skb_header_pointer() returns NULL net/ipv6/netfilter/ip6t_rt.c:111 rt_mt6() error: skb_header_pointer() returns NULL net/ipv4/icmp.c:1076 icmp_build_probe() error: skb_header_pointer() returns NULL net/ipv4/icmp.c:1089 icmp_build_probe() error: skb_header_pointer() returns NULL regards, dan carpenter
