bisecting fixing commit since 7d120bf21c05cbe30a679f0feeca884eeaceb069
building syzkaller on 36650b4b2c942bc382314dce384d311fbadd1208
testing commit 7d120bf21c05cbe30a679f0feeca884eeaceb069
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: f1bb283310cf3fb85c30a7cf9a71abb7ce79b70c514f1b5929555246f3238536
all runs: crashed: general protection fault in tcp_splice_read
testing current HEAD 2950c9c5e0df6bd34af45a5168bbee345e95eae2
testing commit 2950c9c5e0df6bd34af45a5168bbee345e95eae2
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: dae2f07bbb764847c942dd5027d8c6f35dc5785704cb5c461808fafed0b1179a
all runs: crashed: general protection fault in tcp_splice_read
revisions tested: 2, total time: 40m28.674068815s (build: 24m34.294954126s, test: 14m46.82935607s)
the crash still happens on HEAD
commit msg: Linux 4.19.207
crash: general protection fault in tcp_splice_read
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: 1 PID: 14489 Comm: syz-executor.3 Not tainted 4.19.207-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:tcp_splice_read+0x138/0x8d0 net/ipv4/tcp.c:809
Code: fa 48 c1 ea 03 80 3c 02 00 0f 85 18 07 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 64 24 18 49 8d 7c 24 78 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 20 06 00 00 31 c0 41 f6 44 24
RSP: 0018:ffff8881c7367ba8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 1ffff11038e6cf79 RCX: 1ffff1103d23c57f
RDX: 000000000000000f RSI: ffff8881e91e2bd8 RDI: 0000000000000078
RBP: ffff8881c7367cf0 R08: ffff8881e91e2bf8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8881c7367cc8 R15: ffff8881dca56c80
FS:  00007f246e7d4700(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000052c000 CR3: 00000001d4853001 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 smc_splice_read+0x1f6/0x330 net/smc/af_smc.c:1857
 sock_splice_read+0x92/0x120 net/socket.c:924
 do_splice_to+0xe3/0x120 fs/splice.c:881
 do_splice+0xe36/0x12b0 fs/splice.c:1186
 __do_sys_splice fs/splice.c:1428 [inline]
 __se_sys_splice fs/splice.c:1408 [inline]
 __x64_sys_splice+0x248/0x300 fs/splice.c:1408
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x462229
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:00007f246e7d41a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 000000000052bf00 RCX: 0000000000462229
RDX: 0000000000000004 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 0000000000000006 R08: 000000000d86dac9 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004fcdd0 R14: 00000000004b6fb8 R15: 00007f246e7d46bc
Modules linked in:
---[ end trace 77317579dfa33437 ]---
RIP: 0010:tcp_splice_read+0x138/0x8d0 net/ipv4/tcp.c:809
Code: fa 48 c1 ea 03 80 3c 02 00 0f 85 18 07 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 64 24 18 49 8d 7c 24 78 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 20 06 00 00 31 c0 41 f6 44 24
RSP: 0018:ffff8881c7367ba8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 1ffff11038e6cf79 RCX: 1ffff1103d23c57f
RDX: 000000000000000f RSI: ffff8881e91e2bd8 RDI: 0000000000000078
RBP: ffff8881c7367cf0 R08: ffff8881e91e2bf8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8881c7367cc8 R15: ffff8881dca56c80
FS:  00007f246e7d4700(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000005073d4 CR3: 00000001d4853001 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	fa                   	cli
   1:	48 c1 ea 03          	shr    $0x3,%rdx
   5:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   9:	0f 85 18 07 00 00    	jne    0x727
   f:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  16:	fc ff df
  19:	4d 8b 64 24 18       	mov    0x18(%r12),%r12
  1e:	49 8d 7c 24 78       	lea    0x78(%r12),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	0f b6 04 02          	movzbl (%rdx,%rax,1),%eax <-- trapping instruction
  2e:	84 c0                	test   %al,%al
  30:	74 08                	je     0x3a
  32:	3c 03                	cmp    $0x3,%al
  34:	0f 8e 20 06 00 00    	jle    0x65a
  3a:	31 c0                	xor    %eax,%eax
  3c:	41                   	rex.B
  3d:	f6                   	.byte 0xf6
  3e:	44                   	rex.R
  3f:	24                   	.byte 0x24