Re: [syzbot] [fs?] general protection fault in iter_file_splice_write

[syzbot <syzbot+d2125fcb6aa8c4276fd2@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
general protection fault in iter_file_splice_write

netfs: Couldn't get user pages (rc=-14)
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 3 PID: 5391 Comm: syz-executor.0 Not tainted 6.9.0-syzkaller-07370-g33e02dc69afb-dirty #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
RIP: 0010:iter_file_splice_write+0xa28/0x10a0 fs/splice.c:759
Code: 00 00 48 89 fa 48 c1 ea 03 80 3c 2a 00 0f 85 41 05 00 00 4d 8b 6e 10 49 c7 46 10 00 00 00 00 49 8d 7d 08 48 89 fa 48 c1 ea 03 <80> 3c 2a 00 0f 85 16 05 00 00 49 8b 55 08 4c 89 f6 4c 89 ff 41 83
RSP: 0018:ffffc90003927930 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 7fffffffffffefff RCX: ffffffff8209a1ad
RDX: 0000000000000001 RSI: ffffffff8209a071 RDI: 0000000000000008
RBP: dffffc0000000000 R08: 0000000000000006 R09: 0000000000000000
R10: 7fffffffffffefff R11: 0000000000000001 R12: 000000000000009d
R13: 0000000000000000 R14: ffff8880350b5a08 R15: ffff888020f01800
FS:  00007f607512b6c0(0000) GS:ffff88806b300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000026be4000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x19b/0x6d0 fs/splice.c:1164
 splice_direct_to_actor+0x346/0xa40 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0x17e/0x250 fs/splice.c:1233
 do_sendfile+0xaa8/0xdb0 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1362 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0x1da/0x220 fs/read_write.c:1348
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f607447cee9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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:00007f607512b0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f60745abf80 RCX: 00007f607447cee9
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000004
RBP: 00007f60744c949e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000100000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f60745abf80 R15: 00007ffed559a608
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
RIP: 0010:iter_file_splice_write+0xa28/0x10a0 fs/splice.c:759
Code: 00 00 48 89 fa 48 c1 ea 03 80 3c 2a 00 0f 85 41 05 00 00 4d 8b 6e 10 49 c7 46 10 00 00 00 00 49 8d 7d 08 48 89 fa 48 c1 ea 03 <80> 3c 2a 00 0f 85 16 05 00 00 49 8b 55 08 4c 89 f6 4c 89 ff 41 83
RSP: 0018:ffffc90003927930 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 7fffffffffffefff RCX: ffffffff8209a1ad
RDX: 0000000000000001 RSI: ffffffff8209a071 RDI: 0000000000000008
RBP: dffffc0000000000 R08: 0000000000000006 R09: 0000000000000000
R10: 7fffffffffffefff R11: 0000000000000001 R12: 000000000000009d
R13: 0000000000000000 R14: ffff8880350b5a08 R15: ffff888020f01800
FS:  00007f607512b6c0(0000) GS:ffff88806b200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f60745a8000 CR3: 0000000026be4000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	00 00                	add    %al,(%rax)
   2:	48 89 fa             	mov    %rdi,%rdx
   5:	48 c1 ea 03          	shr    $0x3,%rdx
   9:	80 3c 2a 00          	cmpb   $0x0,(%rdx,%rbp,1)
   d:	0f 85 41 05 00 00    	jne    0x554
  13:	4d 8b 6e 10          	mov    0x10(%r14),%r13
  17:	49 c7 46 10 00 00 00 	movq   $0x0,0x10(%r14)
  1e:	00
  1f:	49 8d 7d 08          	lea    0x8(%r13),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 2a 00          	cmpb   $0x0,(%rdx,%rbp,1) <-- trapping instruction
  2e:	0f 85 16 05 00 00    	jne    0x54a
  34:	49 8b 55 08          	mov    0x8(%r13),%rdx
  38:	4c 89 f6             	mov    %r14,%rsi
  3b:	4c 89 ff             	mov    %r15,%rdi
  3e:	41                   	rex.B
  3f:	83                   	.byte 0x83


Tested on:

commit:         33e02dc6 Merge tag 'sound-6.10-rc1' of git://git.kerne..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=161cfadc980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=25544a2faf4bae65
dashboard link: https://syzkaller.appspot.com/bug?extid=d2125fcb6aa8c4276fd2
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=138c6830980000