kernel BUG at include/linux/skbuff.h:LINE! (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 459c5fb4 Merge branch 'mscc-PTP-support'
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13f2d33c600000
kernel config: https://syzkaller.appspot.com/x/.config?x=d4cf1ffb87d590d7
dashboard link: https://syzkaller.appspot.com/bug?extid=eb349eeee854e389c36d
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=111849e2600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1442c25a600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+eb349e...@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at include/linux/skbuff.h:2225!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9030 Comm: syz-executor649 Not tainted 5.3.0-rc3+ #134
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:__skb_pull include/linux/skbuff.h:2225 [inline]
RIP: 0010:__skb_pull include/linux/skbuff.h:2222 [inline]
RIP: 0010:skb_pull_inline include/linux/skbuff.h:2231 [inline]
RIP: 0010:skb_pull+0xea/0x110 net/core/skbuff.c:1902
Code: 9d c8 00 00 00 49 89 dc 49 89 9d c8 00 00 00 e8 9c e5 dd fb 4c 89 e0
5b 41 5c 41 5d 41 5e 5d c3 45 31 e4 eb ea e8 86 e5 dd fb <0f> 0b e8 df 13
18 fc e9 44 ff ff ff e8 d5 13 18 fc eb 8a e8 ee 13
RSP: 0018:ffff88808ac96e10 EFLAGS: 00010293
RAX: ffff88809c546000 RBX: 0000000000000004 RCX: ffffffff8594a3a6
RDX: 0000000000000000 RSI: ffffffff8594a3fa RDI: 0000000000000004
RBP: ffff88808ac96e30 R08: ffff88809c546000 R09: fffffbfff14a8f4f
R10: fffffbfff14a8f4e R11: ffffffff8a547a77 R12: 0000000095e28bcc
R13: ffff88808ac97478 R14: 00000000ffff8880 R15: ffff88808ac97478
FS: 0000555556549880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000100 CR3: 0000000089c3c000 CR4: 00000000001406f0
Call Trace:
sctp_inq_pop+0x2f1/0xd80 net/sctp/inqueue.c:202
sctp_endpoint_bh_rcv+0x184/0x8d0 net/sctp/endpointola.c:385
sctp_inq_push+0x1e4/0x280 net/sctp/inqueue.c:80
sctp_rcv+0x2807/0x3590 net/sctp/input.c:256
sctp6_rcv+0x17/0x30 net/sctp/ipv6.c:1049
ip6_protocol_deliver_rcu+0x2fe/0x1660 net/ipv6/ip6_input.c:397
ip6_input_finish+0x84/0x170 net/ipv6/ip6_input.c:438
NF_HOOK include/linux/netfilter.h:305 [inline]
NF_HOOK include/linux/netfilter.h:299 [inline]
ip6_input+0xe4/0x3f0 net/ipv6/ip6_input.c:447
dst_input include/net/dst.h:442 [inline]
ip6_sublist_rcv_finish+0x98/0x1e0 net/ipv6/ip6_input.c:84
ip6_list_rcv_finish net/ipv6/ip6_input.c:118 [inline]
ip6_sublist_rcv+0x80c/0xcf0 net/ipv6/ip6_input.c:282
ipv6_list_rcv+0x373/0x4b0 net/ipv6/ip6_input.c:316
__netif_receive_skb_list_ptype net/core/dev.c:5049 [inline]
__netif_receive_skb_list_core+0x5fc/0x9d0 net/core/dev.c:5097
__netif_receive_skb_list net/core/dev.c:5149 [inline]
netif_receive_skb_list_internal+0x7eb/0xe60 net/core/dev.c:5244
gro_normal_list.part.0+0x1e/0xb0 net/core/dev.c:5757
gro_normal_list net/core/dev.c:5755 [inline]
gro_normal_one net/core/dev.c:5769 [inline]
napi_frags_finish net/core/dev.c:5782 [inline]
napi_gro_frags+0xa6a/0xea0 net/core/dev.c:5855
tun_get_user+0x2e98/0x3fa0 drivers/net/tun.c:1974
tun_chr_write_iter+0xbd/0x156 drivers/net/tun.c:2020
call_write_iter include/linux/fs.h:1870 [inline]
do_iter_readv_writev+0x5f8/0x8f0 fs/read_write.c:693
do_iter_write fs/read_write.c:970 [inline]
do_iter_write+0x184/0x610 fs/read_write.c:951
vfs_writev+0x1b3/0x2f0 fs/read_write.c:1015
do_writev+0x15b/0x330 fs/read_write.c:1058
__do_sys_writev fs/read_write.c:1131 [inline]
__se_sys_writev fs/read_write.c:1128 [inline]
__x64_sys_writev+0x75/0xb0 fs/read_write.c:1128
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441b10
Code: 05 48 3d 01 f0 ff ff 0f 83 5d 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
00 66 90 83 3d 01 95 29 00 00 75 14 b8 14 00 00 00 0f 05 <48> 3d 01 f0 ff
ff 0f 83 34 09 fc ff c3 48 83 ec 08 e8 ba 2b 00 00
RSP: 002b:00007ffe63706b88 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007ffe63706ba0 RCX: 0000000000441b10
RDX: 0000000000000001 RSI: 00007ffe63706bd0 RDI: 00000000000000f0
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000004
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000122cb
R13: 0000000000402960 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace c37566c1c02066db ]---
RIP: 0010:__skb_pull include/linux/skbuff.h:2225 [inline]
RIP: 0010:__skb_pull include/linux/skbuff.h:2222 [inline]
RIP: 0010:skb_pull_inline include/linux/skbuff.h:2231 [inline]
RIP: 0010:skb_pull+0xea/0x110 net/core/skbuff.c:1902
Code: 9d c8 00 00 00 49 89 dc 49 89 9d c8 00 00 00 e8 9c e5 dd fb 4c 89 e0
5b 41 5c 41 5d 41 5e 5d c3 45 31 e4 eb ea e8 86 e5 dd fb <0f> 0b e8 df 13
18 fc e9 44 ff ff ff e8 d5 13 18 fc eb 8a e8 ee 13
RSP: 0018:ffff88808ac96e10 EFLAGS: 00010293
RAX: ffff88809c546000 RBX: 0000000000000004 RCX: ffffffff8594a3a6
RDX: 0000000000000000 RSI: ffffffff8594a3fa RDI: 0000000000000004
RBP: ffff88808ac96e30 R08: ffff88809c546000 R09: fffffbfff14a8f4f
R10: fffffbfff14a8f4e R11: ffffffff8a547a77 R12: 0000000095e28bcc
R13: ffff88808ac97478 R14: 00000000ffff8880 R15: ffff88808ac97478
FS: 0000555556549880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000100 CR3: 0000000089c3c000 CR4: 00000000001406f0


---
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[syzbot]

syzbot has bisected this bug to:

commit bc389fd101e57b36aacfaec2df8fe479eabb44ea
Author: David S. Miller <da...@davemloft.net>
Date: Tue Jul 2 21:12:30 2019 +0000

Merge branch 'macsec-fix-some-bugs-in-the-receive-path'

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=125c5c4c600000
start commit: 459c5fb4 Merge branch 'mscc-PTP-support'
git tree: net-next
final crash: https://syzkaller.appspot.com/x/report.txt?x=115c5c4c600000
console output: https://syzkaller.appspot.com/x/log.txt?x=165c5c4c600000

kernel config: https://syzkaller.appspot.com/x/.config?x=d4cf1ffb87d590d7
dashboard link: https://syzkaller.appspot.com/bug?extid=eb349eeee854e389c36d

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=111849e2600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1442c25a600000

Reported-by: syzbot+eb349e...@syzkaller.appspotmail.com
Fixes: bc389fd101e5 ("Merge
branch 'macsec-fix-some-bugs-in-the-receive-path'")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Xin Long]

Looks skb_list_del_init() should be called in ip6_sublist_rcv_finish,
as does in ip_sublist_rcv_finish().

[Dmitry Vyukov]

This was recently introduced, right? Only in net-next and linux-next.
Otherwise, is it a remote DoS? If so and if it's present in any
releases, may need a CVE.

[Xin Long]

I need to reproduce and confirm it, will let you know.

[Hillf Danton]

Fri, 16 Aug 2019 11:38:05 -0700

No check no pull.

--- a/net/sctp/inqueue.c
+++ b/net/sctp/inqueue.c
@@ -199,7 +199,12 @@ new_skb:

chunk->chunk_hdr = ch;
chunk->chunk_end = ((__u8 *)ch) + SCTP_PAD4(ntohs(ch->length));
- skb_pull(chunk->skb, sizeof(*ch));
+ if (pskb_may_pull(chunk->skb, sizeof(*ch))) {
+ skb_pull(chunk->skb, sizeof(*ch));
+ } else {
+ sctp_chunk_free(chunk);
+ return NULL;
+ }
chunk->subh.v = NULL; /* Subheader is no longer valid. */

if (chunk->chunk_end + sizeof(*ch) <= skb_tail_pointer(chunk->skb)) {
--

[Xin Long]

The panic could be triggered since the listified RX support for
GRO_NORMAL skbs:
https://patchwork.ozlabs.org/cover/1142808/
(it's only in net-next now, I will post a fix soon)

But the bug itself is not really related with the patch series above.
the issue here is pretty much like what this patch fixed:
https://patchwork.ozlabs.org/patch/942541/
I didn't see a CVE for it, maybe because it was only on net-next too.