Messages in this thread | | | From | Dmitry Vyukov <> | Date | Thu, 6 Sep 2018 21:17:22 +0200 | Subject | Re: KASAN: slab-out-of-bounds Read in _decode_session6 |
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On Thu, Sep 6, 2018 at 7:27 PM, Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: > On Thu, Sep 06, 2018 at 12:00:26AM -0700, Eric Dumazet wrote: >> >> >> On 09/05/2018 08:17 PM, syzbot wrote: >> > syzbot has found a reproducer for the following crash on: >> > >> > HEAD commit:ááá b36fdc6853a3 Merge tag 'gpio-v4.19-2' of git://git.kernel... >> > git tree:áááááá upstream >> > console output: https://syzkaller.appspot.com/x/log.txt?x=164938d1400000 >> > kernel config:á https://syzkaller.appspot.com/x/.config?x=4c7e83258d6e0156 >> > dashboard link: https://syzkaller.appspot.com/bug?extid=acffccec848dc13fe459 >> > compiler:áááááá gcc (GCC) 8.0.1 20180413 (experimental) >> > syz repro:ááááá https://syzkaller.appspot.com/x/repro.syz?x=115f172e400000 >> > C reproducer:áá https://syzkaller.appspot.com/x/repro.c?x=16399be1400000 >> > >> > IMPORTANT: if you fix the bug, please add the following tag to the commit: >> > Reported-by: syzbot+acffccec848dc13fe459@syzkaller.appspotmail.com >> > >> > IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready >> > IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready >> > IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready >> > 8021q: adding VLAN 0 to HW filter on device team0 >> > ================================================================== >> > BUG: KASAN: slab-out-of-bounds in _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 >> > Read of size 1 at addr ffff8801d4a67f07 by task syz-executor092/4673 >> > >> > CPU: 1 PID: 4673 Comm: syz-executor092 Not tainted 4.19.0-rc2+ #223 >> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> > Call Trace: >> > á__dump_stack lib/dump_stack.c:77 [inline] >> > ádump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 >> > áprint_address_description+0x6c/0x20b mm/kasan/report.c:256 >> > ákasan_report_error mm/kasan/report.c:354 [inline] >> > ákasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412 >> > á__asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 >> > á_decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 >> > á__xfrm_decode_session+0x71/0x140 net/xfrm/xfrm_policy.c:2299 >> > áxfrm_decode_session include/net/xfrm.h:1232 [inline] >> > ávti6_tnl_xmit+0x3fc/0x1bb1 net/ipv6/ip6_vti.c:542 >> > á__netdev_start_xmit include/linux/netdevice.h:4287 [inline] >> > ánetdev_start_xmit include/linux/netdevice.h:4296 [inline] >> > áxmit_one net/core/dev.c:3216 [inline] >> > ádev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3232 >> > á__dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3802 >> > ádev_queue_xmit+0x17/0x20 net/core/dev.c:3835 >> > á__bpf_tx_skb net/core/filter.c:2012 [inline] >> > á__bpf_redirect_common net/core/filter.c:2050 [inline] >> > á__bpf_redirect+0x5b7/0xae0 net/core/filter.c:2057 >> > á____bpf_clone_redirect net/core/filter.c:2090 [inline] >> > ábpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2062 >> > ábpf_prog_c39d1ba309a769f7+0xe9e/0x1000 >> > >> > Allocated by task 4673: >> > ásave_stack+0x43/0xd0 mm/kasan/kasan.c:448 >> > áset_track mm/kasan/kasan.c:460 [inline] >> > ákasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 >> > á__do_kmalloc_node mm/slab.c:3682 [inline] >> > á__kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696 >> > á__kmalloc_reserve.isra.41+0x3a/0xe0 net/core/skbuff.c:137 >> > ápskb_expand_head+0x230/0x10e0 net/core/skbuff.c:1463 >> > áskb_ensure_writable+0x3dd/0x640 net/core/skbuff.c:5129 >> > á__bpf_try_make_writable net/core/filter.c:1633 [inline] >> > ábpf_try_make_writable net/core/filter.c:1639 [inline] >> > ábpf_try_make_head_writable net/core/filter.c:1647 [inline] >> > á____bpf_clone_redirect net/core/filter.c:2084 [inline] >> > ábpf_clone_redirect+0x14a/0x490 net/core/filter.c:2062 >> > ábpf_prog_c39d1ba309a769f7+0xe9e/0x1000 >> > >> > Freed by task 3286: >> > ásave_stack+0x43/0xd0 mm/kasan/kasan.c:448 >> > áset_track mm/kasan/kasan.c:460 [inline] >> > á__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 >> > ákasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 >> > á__cache_free mm/slab.c:3498 [inline] >> > ákfree+0xd9/0x210 mm/slab.c:3813 >> > áload_elf_binary+0x2569/0x5610 fs/binfmt_elf.c:1118 >> > ásearch_binary_handler+0x17d/0x570 fs/exec.c:1653 >> > áexec_binprm fs/exec.c:1695 [inline] >> > á__do_execve_file.isra.35+0x15ff/0x2460 fs/exec.c:1819 >> > ádo_execveat_common fs/exec.c:1866 [inline] >> > ádo_execve fs/exec.c:1883 [inline] >> > á__do_sys_execve fs/exec.c:1964 [inline] >> > á__se_sys_execve fs/exec.c:1959 [inline] >> > á__x64_sys_execve+0x8f/0xc0 fs/exec.c:1959 >> > ádo_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 >> > áentry_SYSCALL_64_after_hwframe+0x49/0xbe >> > >> > The buggy address belongs to the object at ffff8801d4a67d00 >> > áwhich belongs to the cache kmalloc-512 of size 512 >> > The buggy address is located 7 bytes to the right of >> > á512-byte region [ffff8801d4a67d00, ffff8801d4a67f00) >> > The buggy address belongs to the page: >> > page:ffffea00075299c0 count:1 mapcount:0 mapping:ffff8801dac00940 index:0x0 >> > flags: 0x2fffc0000000100(slab) >> > raw: 02fffc0000000100 ffffea0007529988 ffffea0007529a48 ffff8801dac00940 >> > raw: 0000000000000000 ffff8801d4a67080 0000000100000006 0000000000000000 >> > page dumped because: kasan: bad access detected >> > >> > Memory state around the buggy address: >> > áffff8801d4a67e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >> > áffff8801d4a67e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >> >> ffff8801d4a67f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> > áááááááááááááááááá ^ >> > áffff8801d4a67f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> > áffff8801d4a68000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> > ================================================================== >> > >> >> >> What about : >> >> diff --git a/net/core/filter.c b/net/core/filter.c >> index aecdeba052d3f0ff3d4f0a33ec36891f9738052c..a662f59786bd0677850c1c60a2c92faa6fb6c5bb 100644 >> --- a/net/core/filter.c >> +++ b/net/core/filter.c >> @@ -2081,7 +2081,7 @@ BPF_CALL_3(bpf_clone_redirect, struct sk_buff *, skb, u32, ifindex, u64, flags) >> * here, we need to free the just generated clone to unclone once >> * again. >> */ >> - ret = bpf_try_make_head_writable(skb); >> + ret = bpf_try_make_head_writable(clone); > > This part is fine. I think the bug is in _decode_session6,
Eric, you arrived to roughly the same conclusion, right?
> but I have a hard time reproducing the issue, so will appreciate > if somebody can test the following patch:
syzbot can: https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches
> From 291f80f212461670d1e0140d06eee3071cf3e1ee Mon Sep 17 00:00:00 2001 > From: Alexei Starovoitov <ast@kernel.org> > Date: Thu, 6 Sep 2018 10:23:29 -0700 > Subject: [PATCH] net/xfrm: fix out-of-bounds packet access > > BUG: KASAN: slab-out-of-bounds in _decode_session6+0x1331/0x14e0 > net/ipv6/xfrm6_policy.c:161 > Read of size 1 at addr ffff8801d882eec7 by task syz-executor1/6667 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 > print_address_description+0x6c/0x20b mm/kasan/report.c:256 > kasan_report_error mm/kasan/report.c:354 [inline] > kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412 > __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 > _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 > __xfrm_decode_session+0x71/0x140 net/xfrm/xfrm_policy.c:2299 > xfrm_decode_session include/net/xfrm.h:1232 [inline] > vti6_tnl_xmit+0x3c3/0x1bc1 net/ipv6/ip6_vti.c:542 > __netdev_start_xmit include/linux/netdevice.h:4313 [inline] > netdev_start_xmit include/linux/netdevice.h:4322 [inline] > xmit_one net/core/dev.c:3217 [inline] > dev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3233 > __dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3803 > dev_queue_xmit+0x17/0x20 net/core/dev.c:3836 > > Reported-by: syzbot+acffccec848dc13fe459@syzkaller.appspotmail.com > Signed-off-by: Alexei Starovoitov <ast@kernel.org> > --- > net/ipv6/xfrm6_policy.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c > index ef3defaf43b9..d35bcf92969c 100644 > --- a/net/ipv6/xfrm6_policy.c > +++ b/net/ipv6/xfrm6_policy.c > @@ -146,8 +146,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse) > fl6->daddr = reverse ? hdr->saddr : hdr->daddr; > fl6->saddr = reverse ? hdr->daddr : hdr->saddr; > > - while (nh + offset + 1 < skb->data || > - pskb_may_pull(skb, nh + offset + 1 - skb->data)) { > + while (nh + offset + sizeof(*exthdr) < skb->data || > + pskb_may_pull(skb, nh + offset + sizeof(*exthdr) - skb->data)) { > nh = skb_network_header(skb); > exthdr = (struct ipv6_opt_hdr *)(nh + offset); > > -- > 2.17.1 > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/20180906172713.cxjoazoo7asqggb3%40ast-mbp.dhcp.thefacebook.com. > For more options, visit https://groups.google.com/d/optout.
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