Re: [syzbot ci] Re: iomap: follow the alignment requirement for iomap_dio_hole_iter()

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2026/7/31 21:11, syzbot ci 写道:
> syzbot ci has tested the following series
> 
> [v1] iomap: follow the alignment requirement for iomap_dio_hole_iter()
> https://lore.kernel.org/all/e69cc8a4a9c3f641b97872b50f04c397880077cd.1785374485.git.wqu@suse.com
> * [PATCH] iomap: follow the alignment requirement for iomap_dio_hole_iter()
> 
> and found the following issue:
> general protection fault in __iomap_dio_rw
> 
> Full report is available here:
> https://ci.syzbot.org/series/81e0fbae-4715-4d62-8e9e-bcd19e46b164
> 
> ***
> 
> general protection fault in __iomap_dio_rw
> 
> tree:      vfs
> URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/vfs/vfs.git
> base:      70c2cbf8600c7d3a622b77e31136b83d6ac7d86c
> arch:      amd64
> compiler:  Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
> config:    https://ci.syzbot.org/builds/8d5fee65-291c-46a2-9f9a-d512f8fad82b/config
> syz repro: https://ci.syzbot.org/findings/c9f79a18-3316-44ec-b805-b805b1c49325/syz_repro
> 
> loop0: rw=2049, sector=53248, nr_sectors = 976 limit=40427
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
> CPU: 0 UID: 0 PID: 5842 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> RIP: 0010:bdev_get_queue include/linux/blkdev.h:1058 [inline]
> RIP: 0010:bdev_logical_block_size include/linux/blkdev.h:1403 [inline]
> RIP: 0010:iomap_dio_alignment fs/iomap/direct-io.c:415 [inline]
> RIP: 0010:iomap_dio_hole_iter fs/iomap/direct-io.c:595 [inline]
> RIP: 0010:iomap_dio_iter fs/iomap/direct-io.c:643 [inline]
> RIP: 0010:__iomap_dio_rw+0x1142/0x2130 fs/iomap/direct-io.c:815
> Code: e2 5a ff 83 e3 08 75 5c e8 ab de 5a ff 48 8b 9c 24 68 01 00 00 48 83 c3 18 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 48 89 df e8 d0 75 c8 ff 48 8b 1b b8 58 01 00 00
> RSP: 0018:ffffc90003fef560 EFLAGS: 00010206
> RAX: 0000000000000003 RBX: 0000000000000018 RCX: dffffc0000000000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffc90003fef860 R08: ffff8881148d8fff R09: 0000000000000000
> R10: ffff8881148d8000 R11: ffffed102291b200 R12: 1ffff920007fdecc
> R13: 0000000000000000 R14: ffff888166b45340 R15: 0000000000001000
> FS:  00007fd77743d6c0(0000) GS:ffff88818d951000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000200000078000 CR3: 000000011606a000 CR4: 00000000000006f0
> Call Trace:
>   <TASK>
>   f2fs_dio_read_iter fs/f2fs/file.c:4887 [inline]

This looks like f2fs is not populating iomap->bdev for holes, which is 
not unreasonable for a hole.

So I need to update iomap_dio_alignment() for @bdev == NULL cases.

Thanks for the report,
Qu


>   f2fs_file_read_iter+0x60b/0x940 fs/f2fs/file.c:4950
>   copy_splice_read+0x5ff/0xaa0 fs/splice.c:362
>   do_splice_read fs/splice.c:979 [inline]
>   splice_direct_to_actor+0x4b6/0xcb0 fs/splice.c:1084
>   do_splice_direct_actor fs/splice.c:1202 [inline]
>   do_splice_direct+0x195/0x290 fs/splice.c:1228
>   do_sendfile+0x52e/0x7c0 fs/read_write.c:1371
>   __do_sys_sendfile64 fs/read_write.c:1432 [inline]
>   __se_sys_sendfile64+0x144/0x1a0 fs/read_write.c:1418
>   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>   do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fd77659df99
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fd77743d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
> RAX: ffffffffffffffda RBX: 00007fd776825fa0 RCX: 00007fd77659df99
> RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000004
> RBP: 00007fd776634ec4 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000800000009 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fd776826038 R14: 00007fd776825fa0 R15: 00007fff168f4a18
>   </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:bdev_get_queue include/linux/blkdev.h:1058 [inline]
> RIP: 0010:bdev_logical_block_size include/linux/blkdev.h:1403 [inline]
> RIP: 0010:iomap_dio_alignment fs/iomap/direct-io.c:415 [inline]
> RIP: 0010:iomap_dio_hole_iter fs/iomap/direct-io.c:595 [inline]
> RIP: 0010:iomap_dio_iter fs/iomap/direct-io.c:643 [inline]
> RIP: 0010:__iomap_dio_rw+0x1142/0x2130 fs/iomap/direct-io.c:815
> Code: e2 5a ff 83 e3 08 75 5c e8 ab de 5a ff 48 8b 9c 24 68 01 00 00 48 83 c3 18 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 48 89 df e8 d0 75 c8 ff 48 8b 1b b8 58 01 00 00
> RSP: 0018:ffffc90003fef560 EFLAGS: 00010206
> RAX: 0000000000000003 RBX: 0000000000000018 RCX: dffffc0000000000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffc90003fef860 R08: ffff8881148d8fff R09: 0000000000000000
> R10: ffff8881148d8000 R11: ffffed102291b200 R12: 1ffff920007fdecc
> R13: 0000000000000000 R14: ffff888166b45340 R15: 0000000000001000
> FS:  00007fd77743d6c0(0000) GS:ffff8882a8f51000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007faa8f64dc80 CR3: 000000011606a000 CR4: 00000000000006f0
> ----------------
> Code disassembly (best guess):
>     0:	e2 5a                	loop   0x5c
>     2:	ff 83 e3 08 75 5c    	incl   0x5c7508e3(%rbx)
>     8:	e8 ab de 5a ff       	call   0xff5adeb8
>     d:	48 8b 9c 24 68 01 00 	mov    0x168(%rsp),%rbx
>    14:	00
>    15:	48 83 c3 18          	add    $0x18,%rbx
>    19:	48 89 d8             	mov    %rbx,%rax
>    1c:	48 c1 e8 03          	shr    $0x3,%rax
>    20:	48 b9 00 00 00 00 00 	movabs $0xdffffc0000000000,%rcx
>    27:	fc ff df
> * 2a:	80 3c 08 00          	cmpb   $0x0,(%rax,%rcx,1) <-- trapping instruction
>    2e:	74 08                	je     0x38
>    30:	48 89 df             	mov    %rbx,%rdi
>    33:	e8 d0 75 c8 ff       	call   0xffc87608
>    38:	48 8b 1b             	mov    (%rbx),%rbx
>    3b:	b8 58 01 00 00       	mov    $0x158,%eax
> 
> 
> ***
> 
> If these findings have caused you to resend the series or submit a
> separate fix, please add the following tag to your commit message:
>    Tested-by: syzbot@syzkaller.appspotmail.com
> 
> ---
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