Messages in this thread Patch in this message | | | Date | Thu, 6 Sep 2018 10:27:18 -0700 | From | Alexei Starovoitov <> | Subject | Re: KASAN: slab-out-of-bounds Read in _decode_session6 |
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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: b36fdc6853a3 Merge tag 'gpio-v4.19-2' of git://git.kernel... > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=164938d1400000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=4c7e83258d6e0156 > > dashboard link: https://syzkaller.appspot.com/bug?extid=acffccec848dc13fe459 > > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=115f172e400000 > > C reproducer: 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: > > __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+0x3fc/0x1bb1 net/ipv6/ip6_vti.c:542 > > __netdev_start_xmit include/linux/netdevice.h:4287 [inline] > > netdev_start_xmit include/linux/netdevice.h:4296 [inline] > > xmit_one net/core/dev.c:3216 [inline] > > dev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3232 > > __dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3802 > > dev_queue_xmit+0x17/0x20 net/core/dev.c:3835 > > __bpf_tx_skb net/core/filter.c:2012 [inline] > > __bpf_redirect_common net/core/filter.c:2050 [inline] > > __bpf_redirect+0x5b7/0xae0 net/core/filter.c:2057 > > ____bpf_clone_redirect net/core/filter.c:2090 [inline] > > bpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2062 > > bpf_prog_c39d1ba309a769f7+0xe9e/0x1000 > > > > Allocated by task 4673: > > save_stack+0x43/0xd0 mm/kasan/kasan.c:448 > > set_track mm/kasan/kasan.c:460 [inline] > > kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 > > __do_kmalloc_node mm/slab.c:3682 [inline] > > __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696 > > __kmalloc_reserve.isra.41+0x3a/0xe0 net/core/skbuff.c:137 > > pskb_expand_head+0x230/0x10e0 net/core/skbuff.c:1463 > > skb_ensure_writable+0x3dd/0x640 net/core/skbuff.c:5129 > > __bpf_try_make_writable net/core/filter.c:1633 [inline] > > bpf_try_make_writable net/core/filter.c:1639 [inline] > > bpf_try_make_head_writable net/core/filter.c:1647 [inline] > > ____bpf_clone_redirect net/core/filter.c:2084 [inline] > > bpf_clone_redirect+0x14a/0x490 net/core/filter.c:2062 > > bpf_prog_c39d1ba309a769f7+0xe9e/0x1000 > > > > Freed by task 3286: > > save_stack+0x43/0xd0 mm/kasan/kasan.c:448 > > set_track mm/kasan/kasan.c:460 [inline] > > __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 > > kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 > > __cache_free mm/slab.c:3498 [inline] > > kfree+0xd9/0x210 mm/slab.c:3813 > > load_elf_binary+0x2569/0x5610 fs/binfmt_elf.c:1118 > > search_binary_handler+0x17d/0x570 fs/exec.c:1653 > > exec_binprm fs/exec.c:1695 [inline] > > __do_execve_file.isra.35+0x15ff/0x2460 fs/exec.c:1819 > > do_execveat_common fs/exec.c:1866 [inline] > > do_execve fs/exec.c:1883 [inline] > > __do_sys_execve fs/exec.c:1964 [inline] > > __se_sys_execve fs/exec.c:1959 [inline] > > __x64_sys_execve+0x8f/0xc0 fs/exec.c:1959 > > do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > The buggy address belongs to the object at ffff8801d4a67d00 > > which belongs to the cache kmalloc-512 of size 512 > > The buggy address is located 7 bytes to the right of > > 512-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: > > ffff8801d4a67e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > ffff8801d4a67e80: 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 > > ^ > > ffff8801d4a67f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > > ffff8801d4a68000: 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, but I have a hard time reproducing the issue, so will appreciate if somebody can test the following patch:
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
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