[syzbot] kernel BUG in pskb_expand_head

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: debe436e77c7 Merge tag 'ext4_for_linus' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17cdbcf1b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=dcce4e862d74e466
dashboard link: https://syzkaller.appspot.com/bug?extid=4c63f36709a642f801c5
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+4c63f3...@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:1695!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 13268 Comm: syz-executor.1 Not tainted 5.15.0-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
RIP: 0010:pskb_expand_head+0xb28/0x1060 net/core/skbuff.c:1695
Code: 8d 75 ff e9 60 fe ff ff e8 75 dd 5a fa 48 c7 c6 a0 60 8c 8a 4c 89 f7 e8 c6 d6 8d fa 0f 0b e8 5f dd 5a fa 0f 0b e8 58 dd 5a fa <0f> 0b e8 51 dd 5a fa 41 81 cc 00 00 02 00 e9 f6 f5 ff ff e8 40 dd
RSP: 0018:ffffc90005a6f2e0 EFLAGS: 00010212
RAX: 0000000000030e8b RBX: ffff88801fa215c0 RCX: ffffc90020bf5000
RDX: 0000000000040000 RSI: ffffffff871c2298 RDI: 0000000000000003
RBP: 00000000ffffffbb R08: 0000000000000001 R09: ffff88801fa2169f
R10: ffffffff871c1842 R11: 0000000000000000 R12: 0000000000000a20
R13: 0000000000000002 R14: 0000000000000001 R15: 0000000000000000
FS: 00007f39135d8700(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020004038 CR3: 0000000065ef5000 CR4: 0000000000150ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
<TASK>
__skb_pad+0x181/0x5f0 net/core/skbuff.c:1929
__skb_put_padto include/linux/skbuff.h:3331 [inline]
skb_put_padto include/linux/skbuff.h:3350 [inline]
eth_skb_pad include/linux/etherdevice.h:584 [inline]
e1000_xmit_frame+0x2de3/0x4650 drivers/net/ethernet/intel/e1000/e1000_main.c:3125
__netdev_start_xmit include/linux/netdevice.h:4987 [inline]
netdev_start_xmit include/linux/netdevice.h:5001 [inline]
xmit_one net/core/dev.c:3590 [inline]
dev_hard_start_xmit+0x1eb/0x920 net/core/dev.c:3606
sch_direct_xmit+0x19f/0xbc0 net/sched/sch_generic.c:342
__dev_xmit_skb net/core/dev.c:3817 [inline]
__dev_queue_xmit+0x149c/0x3630 net/core/dev.c:4194
llc_sap_action_send_test_c+0x22e/0x2c0 net/llc/llc_s_ac.c:144
llc_exec_sap_trans_actions net/llc/llc_sap.c:153 [inline]
llc_sap_next_state net/llc/llc_sap.c:182 [inline]
llc_sap_state_process+0x22a/0x4f0 net/llc/llc_sap.c:209
llc_ui_sendmsg+0x9f3/0x10b0 net/llc/af_llc.c:964
sock_sendmsg_nosec net/socket.c:704 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:724
____sys_sendmsg+0x331/0x810 net/socket.c:2409
___sys_sendmsg+0xf3/0x170 net/socket.c:2463
__sys_sendmmsg+0x195/0x470 net/socket.c:2549
__do_sys_sendmmsg net/socket.c:2578 [inline]
__se_sys_sendmmsg net/socket.c:2575 [inline]
__x64_sys_sendmmsg+0x99/0x100 net/socket.c:2575
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f3916062ae9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f39135d8188 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f3916175f60 RCX: 00007f3916062ae9
RDX: 03fffffffffffeed RSI: 0000000020001380 RDI: 0000000000000005
RBP: 00007f39160bcf6d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe4b72644f R14: 00007f39135d8300 R15: 0000000000022000
</TASK>
Modules linked in:
---[ end trace 518f993fe030bf9b ]---
RIP: 0010:pskb_expand_head+0xb28/0x1060 net/core/skbuff.c:1695
Code: 8d 75 ff e9 60 fe ff ff e8 75 dd 5a fa 48 c7 c6 a0 60 8c 8a 4c 89 f7 e8 c6 d6 8d fa 0f 0b e8 5f dd 5a fa 0f 0b e8 58 dd 5a fa <0f> 0b e8 51 dd 5a fa 41 81 cc 00 00 02 00 e9 f6 f5 ff ff e8 40 dd
RSP: 0018:ffffc90005a6f2e0 EFLAGS: 00010212
RAX: 0000000000030e8b RBX: ffff88801fa215c0 RCX: ffffc90020bf5000
RDX: 0000000000040000 RSI: ffffffff871c2298 RDI: 0000000000000003
RBP: 00000000ffffffbb R08: 0000000000000001 R09: ffff88801fa2169f
R10: ffffffff871c1842 R11: 0000000000000000 R12: 0000000000000a20
R13: 0000000000000002 R14: 0000000000000001 R15: 0000000000000000
FS: 00007f39135d8700(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020004038 CR3: 0000000065ef5000 CR4: 0000000000150ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 434ed2138994 Merge branch 'tc-action-offload'
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1722300db00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7488eea316146357

dashboard link: https://syzkaller.appspot.com/bug?extid=4c63f36709a642f801c5
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14141ca3b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4c63f3...@syzkaller.appspotmail.com

skbuff: skb_over_panic: text:ffffffff88257728 len:4096 put:4096 head:ffff8880769c1400 data:ffff8880769c1400 tail:0x1000 end:0xc0 dev:<NULL>
------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:113!

invalid opcode: 0000 [#1] PREEMPT SMP KASAN

CPU: 0 PID: 13 Comm: ksoftirqd/0 Not tainted 5.16.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:skb_panic+0x16c/0x16e net/core/skbuff.c:113 net/core/skbuff.c:113
Code: f8 4c 8b 4c 24 10 8b 4b 70 41 56 45 89 e8 4c 89 e2 41 57 48 89 ee 48 c7 c7 a0 82 ad 8a ff 74 24 10 ff 74 24 20 e8 13 20 c2 ff <0f> 0b e8 6c 3d 35 f8 4c 8b 64 24 18 e8 f2 9e 7c f8 48 c7 c1 40 8f
RSP: 0018:ffffc90000d279e0 EFLAGS: 00010286
RAX: 000000000000008b RBX: ffff88801c5b8640 RCX: 0000000000000000
RDX: ffff888011938000 RSI: ffffffff815f21d8 RDI: fffff520001a4f2e
RBP: ffffffff8aad8f80 R08: 000000000000008b R09: 0000000000000000
R10: ffffffff815ebf7e R11: 0000000000000000 R12: ffffffff88257728
R13: 0000000000001000 R14: ffffffff8aad8260 R15: 00000000000000c0
FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f14858bf718 CR3: 0000000072e5c000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
skb_over_panic net/core/skbuff.c:118 [inline]
skb_over_panic net/core/skbuff.c:118 [inline] net/core/skbuff.c:1986
skb_put.cold+0x24/0x24 net/core/skbuff.c:1986 net/core/skbuff.c:1986
isotp_rcv_cf net/can/isotp.c:570 [inline]
isotp_rcv_cf net/can/isotp.c:570 [inline] net/can/isotp.c:668
isotp_rcv+0xa38/0x1e30 net/can/isotp.c:668 net/can/isotp.c:668
deliver net/can/af_can.c:574 [inline]
deliver net/can/af_can.c:574 [inline] net/can/af_can.c:635
can_rcv_filter+0x445/0x8d0 net/can/af_can.c:635 net/can/af_can.c:635
can_receive+0x31d/0x580 net/can/af_can.c:665 net/can/af_can.c:665
can_rcv+0x120/0x1c0 net/can/af_can.c:696 net/can/af_can.c:696
__netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5350 net/core/dev.c:5350
__netif_receive_skb+0x24/0x1b0 net/core/dev.c:5464 net/core/dev.c:5464
process_backlog+0x2a5/0x6c0 net/core/dev.c:5796 net/core/dev.c:5796
__napi_poll+0xaf/0x440 net/core/dev.c:6364 net/core/dev.c:6364
napi_poll net/core/dev.c:6431 [inline]
napi_poll net/core/dev.c:6431 [inline] net/core/dev.c:6518
net_rx_action+0x801/0xb40 net/core/dev.c:6518 net/core/dev.c:6518
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558 kernel/softirq.c:558
run_ksoftirqd kernel/softirq.c:921 [inline]
run_ksoftirqd kernel/softirq.c:921 [inline] kernel/softirq.c:913
run_ksoftirqd+0x2d/0x60 kernel/softirq.c:913 kernel/softirq.c:913
smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164 kernel/smpboot.c:164
kthread+0x405/0x4f0 kernel/kthread.c:327 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 arch/x86/entry/entry_64.S:295
</TASK>
Modules linked in:
---[ end trace 076cfcb09686117c ]---
RIP: 0010:skb_panic+0x16c/0x16e net/core/skbuff.c:113 net/core/skbuff.c:113
Code: f8 4c 8b 4c 24 10 8b 4b 70 41 56 45 89 e8 4c 89 e2 41 57 48 89 ee 48 c7 c7 a0 82 ad 8a ff 74 24 10 ff 74 24 20 e8 13 20 c2 ff <0f> 0b e8 6c 3d 35 f8 4c 8b 64 24 18 e8 f2 9e 7c f8 48 c7 c1 40 8f
RSP: 0018:ffffc90000d279e0 EFLAGS: 00010286
RAX: 000000000000008b RBX: ffff88801c5b8640 RCX: 0000000000000000
RDX: ffff888011938000 RSI: ffffffff815f21d8 RDI: fffff520001a4f2e
RBP: ffffffff8aad8f80 R08: 000000000000008b R09: 0000000000000000
R10: ffffffff815ebf7e R11: 0000000000000000 R12: ffffffff88257728
R13: 0000000000001000 R14: ffffffff8aad8260 R15: 00000000000000c0
FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f14858bf718 CR3: 0000000072e5c000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

[syzbot]

syzbot has bisected this issue to:

commit e4b8954074f6d0db01c8c97d338a67f9389c042f
Author: Eric Dumazet <edum...@google.com>
Date: Tue Dec 7 01:30:37 2021 +0000

netlink: add net device refcount tracker to struct ethnl_req_info

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=109e6fcbb00000
start commit: 434ed2138994 Merge branch 'tc-action-offload'
git tree: net-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=129e6fcbb00000
console output: https://syzkaller.appspot.com/x/log.txt?x=149e6fcbb00000

kernel config: https://syzkaller.appspot.com/x/.config?x=7488eea316146357
dashboard link: https://syzkaller.appspot.com/bug?extid=4c63f36709a642f801c5

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14141ca3b00000

Reported-by: syzbot+4c63f3...@syzkaller.appspotmail.com
Fixes: e4b8954074f6 ("netlink: add net device refcount tracker to struct ethnl_req_info")

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

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: c9e6606c7fe9 Linux 5.16-rc8
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=148351c3b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=32f9fa260d7413b4

dashboard link: https://syzkaller.appspot.com/bug?extid=4c63f36709a642f801c5
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15435e2bb00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f4508db00000

The issue was bisected to:

commit e4b8954074f6d0db01c8c97d338a67f9389c042f
Author: Eric Dumazet <edum...@google.com>
Date: Tue Dec 7 01:30:37 2021 +0000

netlink: add net device refcount tracker to struct ethnl_req_info

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=109e6fcbb00000

final oops: https://syzkaller.appspot.com/x/report.txt?x=129e6fcbb00000
console output: https://syzkaller.appspot.com/x/log.txt?x=149e6fcbb00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4c63f3...@syzkaller.appspotmail.com

Fixes: e4b8954074f6 ("netlink: add net device refcount tracker to struct ethnl_req_info")

skbuff: skb_over_panic: text:ffffffff88235fb8 len:4096 put:4096 head:ffff888021cb8400 data:ffff888021cb8400 tail:0x1000 end:0xc0 dev:<NULL>
------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:113!

invalid opcode: 0000 [#1] PREEMPT SMP KASAN

CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 5.16.0-rc8-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:skb_panic+0x16c/0x16e net/core/skbuff.c:113

Code: f8 4c 8b 4c 24 10 8b 4b 70 41 56 45 89 e8 4c 89 e2 41 57 48 89 ee 48 c7 c7 e0 4b ad 8a ff 74 24 10 ff 74 24 20 e8 6e 24 c2 ff <0f> 0b e8 74 92 38 f8 4c 8b 64 24 18 e8 da 47 7f f8 48 c7 c1 80 58
RSP: 0018:ffffc90000d979e0 EFLAGS: 00010286
RAX: 000000000000008b RBX: ffff888021ccb500 RCX: 0000000000000000
RDX: ffff88801196d700 RSI: ffffffff815f0948 RDI: fffff520001b2f2e
RBP: ffffffff8aad58c0 R08: 000000000000008b R09: 0000000000000000
R10: ffffffff815ea6ee R11: 0000000000000000 R12: ffffffff88235fb8
R13: 0000000000001000 R14: ffffffff8aad4ba0 R15: 00000000000000c0
FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f886c8cc718 CR3: 000000007ad6d000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
skb_over_panic net/core/skbuff.c:118 [inline]

skb_put.cold+0x24/0x24 net/core/skbuff.c:1990
isotp_rcv_cf net/can/isotp.c:570 [inline]
isotp_rcv+0xa38/0x1e30 net/can/isotp.c:668
deliver net/can/af_can.c:574 [inline]
can_rcv_filter+0x445/0x8d0 net/can/af_can.c:635
can_receive+0x31d/0x580 net/can/af_can.c:665
can_rcv+0x120/0x1c0 net/can/af_can.c:696
__netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5465
__netif_receive_skb+0x24/0x1b0 net/core/dev.c:5579
process_backlog+0x2a5/0x6c0 net/core/dev.c:6455
__napi_poll+0xaf/0x440 net/core/dev.c:7023
napi_poll net/core/dev.c:7090 [inline]
net_rx_action+0x801/0xb40 net/core/dev.c:7177
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558
run_ksoftirqd kernel/softirq.c:921 [inline]
run_ksoftirqd+0x2d/0x60 kernel/softirq.c:913
smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Modules linked in:
---[ end trace 9f06028ec4daf4be ]---

RIP: 0010:skb_panic+0x16c/0x16e net/core/skbuff.c:113

Code: f8 4c 8b 4c 24 10 8b 4b 70 41 56 45 89 e8 4c 89 e2 41 57 48 89 ee 48 c7 c7 e0 4b ad 8a ff 74 24 10 ff 74 24 20 e8 6e 24 c2 ff <0f> 0b e8 74 92 38 f8 4c 8b 64 24 18 e8 da 47 7f f8 48 c7 c1 80 58
RSP: 0018:ffffc90000d979e0 EFLAGS: 00010286
RAX: 000000000000008b RBX: ffff888021ccb500 RCX: 0000000000000000
RDX: ffff88801196d700 RSI: ffffffff815f0948 RDI: fffff520001b2f2e
RBP: ffffffff8aad58c0 R08: 000000000000008b R09: 0000000000000000
R10: ffffffff815ea6ee R11: 0000000000000000 R12: ffffffff88235fb8
R13: 0000000000001000 R14: ffffffff8aad4ba0 R15: 00000000000000c0
FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f886c8cc718 CR3: 000000007ad6d000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

[Marc Kleine-Budde]

On 19.12.2021 16:19:20, syzbot wrote:
> skb_over_panic net/core/skbuff.c:118 [inline]
> skb_over_panic net/core/skbuff.c:118 [inline] net/core/skbuff.c:1986
> skb_put.cold+0x24/0x24 net/core/skbuff.c:1986 net/core/skbuff.c:1986
> isotp_rcv_cf net/can/isotp.c:570 [inline]
> isotp_rcv_cf net/can/isotp.c:570 [inline] net/can/isotp.c:668
> isotp_rcv+0xa38/0x1e30 net/can/isotp.c:668 net/can/isotp.c:668

> struct tpcon {
> int idx;
> int len;
^^^
> u32 state;
> u8 bs;
> u8 sn;
> u8 ll_dl;
> u8 buf[MAX_MSG_LENGTH + 1];
> };
>
> static int isotp_rcv_ff(struct sock *sk, struct canfd_frame *cf, int ae)
> {

[...]

> /* Check for FF_DL escape sequence supporting 32 bit PDU length */
> if (so->rx.len) {
> ff_pci_sz = FF_PCI_SZ12;
> } else {
> /* FF_DL = 0 => get real length from next 4 bytes */
> so->rx.len = cf->data[ae + 2] << 24;
> so->rx.len += cf->data[ae + 3] << 16;
> so->rx.len += cf->data[ae + 4] << 8;
> so->rx.len += cf->data[ae + 5];
> ff_pci_sz = FF_PCI_SZ32;
> }

Full 32 Bit PDUs don't work with struct tpcon::len being an "int". I
think converting it to "unsigned int" should be done.

[...]

> }
>
> static int isotp_rcv_cf(struct sock *sk, struct canfd_frame *cf, int ae,
> struct sk_buff *skb)
> {
> struct isotp_sock *so = isotp_sk(sk);
> struct sk_buff *nskb;
> int i;
>
> if (so->rx.state != ISOTP_WAIT_DATA)
> return 0;
>
> /* drop if timestamp gap is less than force_rx_stmin nano secs */
> if (so->opt.flags & CAN_ISOTP_FORCE_RXSTMIN) {
> if (ktime_to_ns(ktime_sub(skb->tstamp, so->lastrxcf_tstamp)) <
> so->force_rx_stmin)
> return 0;
>
> so->lastrxcf_tstamp = skb->tstamp;
> }
>
> hrtimer_cancel(&so->rxtimer);
>
> /* CFs are never longer than the FF */
> if (cf->len > so->rx.ll_dl)
> return 1;
>
> /* CFs have usually the LL_DL length */
> if (cf->len < so->rx.ll_dl) {
> /* this is only allowed for the last CF */
> if (so->rx.len - so->rx.idx > so->rx.ll_dl - ae - N_PCI_SZ)
> return 1;
> }
>
> if ((cf->data[ae] & 0x0F) != so->rx.sn) {
> /* wrong sn detected - report 'illegal byte sequence' */
> sk->sk_err = EILSEQ;
> if (!sock_flag(sk, SOCK_DEAD))
> sk_error_report(sk);
>
> /* reset rx state */
> so->rx.state = ISOTP_IDLE;
> return 1;
> }
> so->rx.sn++;
> so->rx.sn %= 16;
>
> for (i = ae + N_PCI_SZ; i < cf->len; i++) {
> so->rx.buf[so->rx.idx++] = cf->data[i];
> if (so->rx.idx >= so->rx.len)
> break;
> }
>
> if (so->rx.idx >= so->rx.len) {
> /* we are done */
> so->rx.state = ISOTP_IDLE;
>
> if ((so->opt.flags & ISOTP_CHECK_PADDING) &&
> check_pad(so, cf, i + 1, so->opt.rxpad_content)) {
> /* malformed PDU - report 'not a data message' */
> sk->sk_err = EBADMSG;
> if (!sock_flag(sk, SOCK_DEAD))
> sk_error_report(sk);
> return 1;
> }
>
> nskb = alloc_skb(so->rx.len, gfp_any());
> if (!nskb)
> return 1;
>
> memcpy(skb_put(nskb, so->rx.len), so->rx.buf,
^^^^^^^
> so->rx.len);

This is where the skb_over_panic() happens.

regards,
Marc

--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |

[Oliver Hartkopp]

Thanks Marc!

Yes I went to this piece of code too - but was not able to find anything
wrong, as the values at this point should be far(!!) away from INT_MAX.

Due to this check in isotp_rcv_ff():

if (so->rx.len > MAX_MSG_LENGTH) { ... exit

And MAX_MSG_LENGTH is define as 8200.

Btw. making tpcon:len an unsigned int is really the solution to this!
Which makes the above if-statement act correctly also with values like
0x80001234.

m(

Thanks for the finding!

Best regards,
Oliver

[Eric Dumazet]

On Wed, Jan 5, 2022 at 3:20 AM syzbot
<syzbot+4c63f3...@syzkaller.appspotmail.com> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: c9e6606c7fe9 Linux 5.16-rc8
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=148351c3b00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=32f9fa260d7413b4
> dashboard link: https://syzkaller.appspot.com/bug?extid=4c63f36709a642f801c5
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15435e2bb00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f4508db00000
>

This C repro looks legit, bug should be in CAN layer.

> The issue was bisected to:
>
> commit e4b8954074f6d0db01c8c97d338a67f9389c042f
> Author: Eric Dumazet <edum...@google.com>
> Date: Tue Dec 7 01:30:37 2021 +0000
>
> netlink: add net device refcount tracker to struct ethnl_req_info

Ignore this bisection, an unrelated commit whent in its way.

[Marc Kleine-Budde]

On 05.01.2022 05:59:35, Eric Dumazet wrote:
> On Wed, Jan 5, 2022 at 3:20 AM syzbot
> <syzbot+4c63f3...@syzkaller.appspotmail.com> wrote:
> >
> > syzbot has found a reproducer for the following issue on:
> >
> > HEAD commit: c9e6606c7fe9 Linux 5.16-rc8
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=148351c3b00000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=32f9fa260d7413b4
> > dashboard link: https://syzkaller.appspot.com/bug?extid=4c63f36709a642f801c5
> > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15435e2bb00000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f4508db00000
> >
>
> This C repro looks legit, bug should be in CAN layer.

ACK - it's bug in CAN's ISOTP

> > The issue was bisected to:
> >
> > commit e4b8954074f6d0db01c8c97d338a67f9389c042f
> > Author: Eric Dumazet <edum...@google.com>
> > Date: Tue Dec 7 01:30:37 2021 +0000
> >
> > netlink: add net device refcount tracker to struct ethnl_req_info
>
> Ignore this bisection, an unrelated commit whent in its way.

ACK - We have a RFC fix for this:

https://lore.kernel.org/all/20220105132429...@pengutronix.de