bisecting fixing commit since c63ee2939dc1c6eee6c544af1b4ab441490bfe6e
building syzkaller on 598ca6c8b8766304c3b2865e38f5f301c39bd299
testing commit c63ee2939dc1c6eee6c544af1b4ab441490bfe6e with gcc (GCC) 8.1.0
kernel signature: a1a6ec09ea5846cf09eebb42b215521c38745b24c9f85c9490180c6be403cff4
run #0: crashed: general protection fault in skb_unlink
run #1: crashed: general protection fault in skb_unlink
run #2: crashed: general protection fault in skb_unlink
run #3: crashed: general protection fault in skb_unlink
run #4: crashed: general protection fault in requeue_rx_msgs
run #5: crashed: general protection fault in skb_unlink
run #6: crashed: general protection fault in skb_unlink
run #7: crashed: general protection fault in skb_unlink
run #8: crashed: general protection fault in skb_unlink
run #9: crashed: general protection fault in requeue_rx_msgs
testing current HEAD 3fc898571b974f9a05e4e5c1fe17b18548207091
testing commit 3fc898571b974f9a05e4e5c1fe17b18548207091 with gcc (GCC) 8.1.0
kernel signature: 48d19370d17e4532775ac5dff639ebd3e2e83689c59b816b16be4a3fbcf0efce
run #0: crashed: general protection fault in skb_unlink
run #1: crashed: general protection fault in requeue_rx_msgs
run #2: crashed: general protection fault in skb_unlink
run #3: crashed: general protection fault in skb_unlink
run #4: crashed: general protection fault in skb_unlink
run #5: crashed: general protection fault in skb_unlink
run #6: crashed: general protection fault in skb_unlink
run #7: crashed: general protection fault in requeue_rx_msgs
run #8: crashed: general protection fault in skb_unlink
run #9: crashed: general protection fault in skb_unlink
revisions tested: 2, total time: 22m51.797359147s (build: 16m26.357302815s, test: 6m2.07282334s)
the crash still happens on HEAD
commit msg: Linux 4.19.128
crash: general protection fault in skb_unlink
nf_conntrack: default automatic helper assignment has been turned off for security reasons and CT-based  firewall rule not found. Use the iptables CT target to attach helpers instead.
nf_conntrack: default automatic helper assignment has been turned off for security reasons and CT-based  firewall rule not found. Use the iptables CT target to attach helpers instead.
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 7329 Comm: syz-executor.0 Not tainted 4.19.128-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__write_once_size include/linux/compiler.h:220 [inline]
RIP: 0010:__skb_unlink include/linux/skbuff.h:1902 [inline]
RIP: 0010:skb_unlink+0xbb/0x160 net/core/skbuff.c:2945
Code: 00 00 49 8d 7d 08 4c 8b 63 08 48 ba 00 00 00 00 00 fc ff df 48 c7 43 08 00 00 00 00 48 89 f9 48 c7 03 00 00 00 00 48 c1 e9 03 <80> 3c 11 00 75 5b 4c 89 e1 4d 89 65 08 48 ba 00 00 00 00 00 fc ff
RSP: 0018:ffff888093a47840 EFLAGS: 00010002
RAX: 0000000000000286 RBX: ffff888092aade40 RCX: 0000000000000001
RDX: dffffc0000000000 RSI: 0000000000000004 RDI: 0000000000000008
RBP: ffff888093a47868 R08: ffffed10125095dd R09: ffffed10125095dc
R10: ffffed10125095dc R11: ffff88809284aee3 R12: 0000000000000000
R13: 0000000000000000 R14: ffff88809284aee0 R15: 0000000000000000
FS:  00007f9d9f0bd700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa638a7ddb8 CR3: 00000000938a2000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 kcm_recvmsg+0x3a5/0x5a0 net/kcm/kcmsock.c:1160
 sock_recvmsg_nosec+0x7b/0xd0 net/socket.c:795
 ___sys_recvmsg+0x219/0x500 net/socket.c:2277
 __sys_recvmmsg+0x21d/0x650 net/socket.c:2389
 do_sys_recvmmsg+0x111/0x130 net/socket.c:2465
 __do_sys_recvmmsg net/socket.c:2483 [inline]
 __se_sys_recvmmsg net/socket.c:2479 [inline]
 __x64_sys_recvmmsg+0xb9/0x150 net/socket.c:2479
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a639
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f9d9f0bcc78 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 000000000045a639
RDX: 0400000000000310 RSI: 0000000020003540 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9d9f0bd6d4
R13: 00000000004c82f0 R14: 00000000004de6e0 R15: 00000000ffffffff
Modules linked in:
---[ end trace 537e00fd932b238c ]---
RIP: 0010:__write_once_size include/linux/compiler.h:220 [inline]
RIP: 0010:__skb_unlink include/linux/skbuff.h:1902 [inline]
RIP: 0010:skb_unlink+0xbb/0x160 net/core/skbuff.c:2945
Code: 00 00 49 8d 7d 08 4c 8b 63 08 48 ba 00 00 00 00 00 fc ff df 48 c7 43 08 00 00 00 00 48 89 f9 48 c7 03 00 00 00 00 48 c1 e9 03 <80> 3c 11 00 75 5b 4c 89 e1 4d 89 65 08 48 ba 00 00 00 00 00 fc ff
RSP: 0018:ffff888093a47840 EFLAGS: 00010002
RAX: 0000000000000286 RBX: ffff888092aade40 RCX: 0000000000000001
RDX: dffffc0000000000 RSI: 0000000000000004 RDI: 0000000000000008
RBP: ffff888093a47868 R08: ffffed10125095dd R09: ffffed10125095dc
R10: ffffed10125095dc R11: ffff88809284aee3 R12: 0000000000000000
R13: 0000000000000000 R14: ffff88809284aee0 R15: 0000000000000000
FS:  00007f9d9f0bd700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa638a7ddb8 CR3: 00000000938a2000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400