[syzbot] [tipc?] kernel BUG in __pskb_pull_tail

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 96b6fcc0ee41 Merge branch 'net-dsa-cleanup-eee-part-1'
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13a74d44580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1362a5aee630ff34
dashboard link: https://syzkaller.appspot.com/bug?extid=4f66250f6663c0c1d67e
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15eb0730580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=117844f8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c62feec036f0/disk-96b6fcc0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0dd481b2d92e/vmlinux-96b6fcc0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7f647dfdfac4/bzImage-96b6fcc0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4f6625...@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:2849!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 0 UID: 0 PID: 6230 Comm: syz-executor132 Not tainted 6.13.0-rc1-syzkaller-00407-g96b6fcc0ee41 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
RIP: 0010:__pskb_pull_tail+0x1568/0x1570 net/core/skbuff.c:2848
Code: 38 c1 0f 8c 32 f1 ff ff 4c 89 f7 e8 92 96 74 f8 e9 25 f1 ff ff e8 e8 ae 09 f8 48 8b 5c 24 08 e9 eb fb ff ff e8 d9 ae 09 f8 90 <0f> 0b 66 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90004cbef30 EFLAGS: 00010293
RAX: ffffffff8995c347 RBX: 00000000fffffff2 RCX: ffff88802cf45a00
RDX: 0000000000000000 RSI: 00000000fffffff2 RDI: 0000000000000000
RBP: ffff88807df0c06a R08: ffffffff8995b084 R09: 1ffff1100fbe185c
R10: dffffc0000000000 R11: ffffed100fbe185d R12: ffff888076e85d50
R13: ffff888076e85c80 R14: ffff888076e85cf4 R15: ffff888076e85c80
FS: 00007f0dca6ea6c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0dca6ead58 CR3: 00000000119da000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
skb_cow_data+0x2da/0xcb0 net/core/skbuff.c:5284
tipc_aead_decrypt net/tipc/crypto.c:894 [inline]
tipc_crypto_rcv+0x402/0x24e0 net/tipc/crypto.c:1844
tipc_rcv+0x57e/0x12a0 net/tipc/node.c:2109
tipc_l2_rcv_msg+0x2bd/0x450 net/tipc/bearer.c:668
__netif_receive_skb_list_ptype net/core/dev.c:5720 [inline]
__netif_receive_skb_list_core+0x8b7/0x980 net/core/dev.c:5762
__netif_receive_skb_list net/core/dev.c:5814 [inline]
netif_receive_skb_list_internal+0xa51/0xe30 net/core/dev.c:5905
gro_normal_list include/net/gro.h:515 [inline]
napi_complete_done+0x2b5/0x870 net/core/dev.c:6256
napi_complete include/linux/netdevice.h:567 [inline]
tun_get_user+0x2ea0/0x4890 drivers/net/tun.c:1982
tun_chr_write_iter+0x10d/0x1f0 drivers/net/tun.c:2057
do_iter_readv_writev+0x600/0x880
vfs_writev+0x376/0xba0 fs/read_write.c:1050
do_writev+0x1b6/0x360 fs/read_write.c:1096
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0dca751f69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 31 1a 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0dca6ea218 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f0dca7dc438 RCX: 00007f0dca751f69
RDX: 0000000000000002 RSI: 00000000200001c0 RDI: 0000000000000004
RBP: 00007f0dca7dc430 R08: 00007ffdc30a1047 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f0dca7a92a4
R13: 006e75742f74656e R14: 74656e2f7665642f R15: 796c27468c04729a
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__pskb_pull_tail+0x1568/0x1570 net/core/skbuff.c:2848
Code: 38 c1 0f 8c 32 f1 ff ff 4c 89 f7 e8 92 96 74 f8 e9 25 f1 ff ff e8 e8 ae 09 f8 48 8b 5c 24 08 e9 eb fb ff ff e8 d9 ae 09 f8 90 <0f> 0b 66 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90004cbef30 EFLAGS: 00010293
RAX: ffffffff8995c347 RBX: 00000000fffffff2 RCX: ffff88802cf45a00
RDX: 0000000000000000 RSI: 00000000fffffff2 RDI: 0000000000000000
RBP: ffff88807df0c06a R08: ffffffff8995b084 R09: 1ffff1100fbe185c
R10: dffffc0000000000 R11: ffffed100fbe185d R12: ffff888076e85d50
R13: ffff888076e85c80 R14: ffff888076e85cf4 R15: ffff888076e85c80
FS: 00007f0dca6ea6c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0dca6ead58 CR3: 00000000119da000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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[syzbot]

syzbot has bisected this issue to:

commit de4f5fed3f231a8ff4790bf52975f847b95b85ea
Author: Jens Axboe <ax...@kernel.dk>
Date: Wed Mar 29 14:52:15 2023 +0000

iov_iter: add iter_iovec() helper

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17424730580000
start commit: 96b6fcc0ee41 Merge branch 'net-dsa-cleanup-eee-part-1'
git tree: net-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=14c24730580000
console output: https://syzkaller.appspot.com/x/log.txt?x=10c24730580000

kernel config: https://syzkaller.appspot.com/x/.config?x=1362a5aee630ff34
dashboard link: https://syzkaller.appspot.com/bug?extid=4f66250f6663c0c1d67e

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=166944f8580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1287ecdf980000

Reported-by: syzbot+4f6625...@syzkaller.appspotmail.com
Fixes: de4f5fed3f23 ("iov_iter: add iter_iovec() helper")

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

[Eric Dumazet]

Great, thanks syzbot.

Patch is under review :

https://patchwork.kernel.org/project/netdevbpf/patch/20241212222247.7...@google.com/

[Hillf Danton]

On Thu, 12 Dec 2024 14:20:26 -0800

> syzbot found the following issue on:
>
> HEAD commit: 96b6fcc0ee41 Merge branch 'net-dsa-cleanup-eee-part-1'
> git tree: net-next

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=117844f8580000

Test fix (https://patchwork.kernel.org/project/netdevbpf/patch/20241212222247.7...@google.com/ )

#syz test

--- x/drivers/net/tun.c
+++ y/drivers/net/tun.c
@@ -1485,7 +1485,7 @@ static struct sk_buff *tun_napi_alloc_fr
skb->truesize += skb->data_len;

for (i = 1; i < it->nr_segs; i++) {
- const struct iovec *iov = iter_iov(it);
+ const struct iovec *iov = iter_iov(it) + i;
size_t fragsz = iov->iov_len;
struct page *page;
void *frag;
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+4f6625...@syzkaller.appspotmail.com
Tested-by: syzbot+4f6625...@syzkaller.appspotmail.com

Tested on:

commit: 2c27c766 Merge branch 'devmem-tcp-fixes'
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=121ac730580000
kernel config: https://syzkaller.appspot.com/x/.config?x=fee25f93665c89ac

dashboard link: https://syzkaller.appspot.com/bug?extid=4f66250f6663c0c1d67e
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1042a4f8580000

Note: testing is done by a robot and is best-effort only.