bisecting fixing commit since 7d120bf21c05cbe30a679f0feeca884eeaceb069
building syzkaller on 36650b4b2c942bc382314dce384d311fbadd1208
testing commit 7d120bf21c05cbe30a679f0feeca884eeaceb069
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 48fd38d248c8385ca0f32c03a808d8535e3bb85468387b7d3ee37f00107370d9
all runs: crashed: general protection fault in tcp_splice_read
testing current HEAD e23d55af0e1fca9be5c99f0c37d48b289f4d6489
testing commit e23d55af0e1fca9be5c99f0c37d48b289f4d6489
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 10acbf62d68b1e0627fd7b6693d455a039c8ebe3483e42269e4f3832c8066ca1
all runs: crashed: general protection fault in tcp_splice_read
revisions tested: 2, total time: 36m59.543667439s (build: 21m17.243441987s, test: 14m44.311285458s)
the crash still happens on HEAD
commit msg: Linux 4.19.205
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: 0 PID: 26086 Comm: syz-executor.4 Not tainted 4.19.205-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:ffff8881c5ec7ba8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 1ffff11038bd8f79 RCX: 1ffff1103aeaf1df
RDX: 000000000000000f RSI: ffff8881d7578ed8 RDI: 0000000000000078
RBP: ffff8881c5ec7cf0 R08: ffff8881d7578ef8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8881c5ec7cc8 R15: ffff8881f4724240
FS:  00007f69d3c6d700(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000080 CR3: 00000001e20a3001 CR4: 00000000001606f0
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:00007f69d3c6d1a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 000000000052bfa8 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: 00007f69d3c6d6bc
Modules linked in:
---[ end trace 220c5d5843b6d403 ]---
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:ffff8881c5ec7ba8 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 1ffff11038bd8f79 RCX: 1ffff1103aeaf1df
RDX: 000000000000000f RSI: ffff8881d7578ed8 RDI: 0000000000000078
RBP: ffff8881c5ec7cf0 R08: ffff8881d7578ef8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8881c5ec7cc8 R15: ffff8881f4724240
FS:  00007f69d3c6d700(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000562bfbc20140 CR3: 00000001e20a3002 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