Re: [syzbot] [block?] BUG: unable to handle kernel NULL pointer dereference in __bio_release_pages

Jens Axboe
2024-01-16T20:00:30Z

On 1/16/24 11:42 AM, Matthew Wilcox wrote:
> On Tue, Jan 16, 2024 at 11:00:52AM -0700, Jens Axboe wrote:
>> On 1/16/24 2:57 AM, syzbot wrote:
>>> pstate: 10000005 (nzcV daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>> pc : _compound_head include/linux/page-flags.h:247 [inline]
>>> pc : bio_first_folio include/linux/bio.h:289 [inline]
>>> pc : __bio_release_pages+0x100/0x73c block/bio.c:1153
>>> lr : bio_release_pages include/linux/bio.h:508 [inline]
>>> lr : blkdev_bio_end_io+0x2a0/0x3f0 block/fops.c:157
>>> sp : ffff800089a375e0
>>> x29: ffff800089a375e0 x28: 1fffe0000162e879 x27: ffff00000b1743c0
>>> x26: ffff00000b1743c8 x25: 000000000000000a x24: 1fffe000015a9e12
>>> x23: ffff00000ad4f094 x22: ffff00000f496600 x21: 1fffe0000162e87a
>>> x20: 0000000000000004 x19: 0000000000000000 x18: ffff00000b174432
>>> x17: ffff00000b174438 x16: ffff00000f948008 x15: 1fffe0000162e886
>>> x14: ffff00000b1743d4 x13: 00000000f1f1f1f1 x12: ffff6000015a9e13
>>> x11: 1fffe000015a9e12 x10: ffff6000015a9e12 x9 : dfff800000000000
>>> x8 : ffff00000b1743d4 x7 : 0000000041b58ab3 x6 : 1ffff00011346ed0
>>> x5 : ffff700011346ed0 x4 : 00000000f1f1f1f1 x3 : 000000000000f1f1
>>> x2 : 0000000000000001 x1 : dfff800000000000 x0 : 0000000000000008
>>> Call trace:
>>> _compound_head include/linux/page-flags.h:247 [inline]
>>> bio_first_folio include/linux/bio.h:289 [inline]
>>> __bio_release_pages+0x100/0x73c block/bio.c:1153
>>> bio_release_pages include/linux/bio.h:508 [inline]
>>> blkdev_bio_end_io+0x2a0/0x3f0 block/fops.c:157
>>> bio_endio+0x4a4/0x618 block/bio.c:1608
>>
>> This looks to be caused by:
>>
>> commit 1b151e2435fc3a9b10c8946c6aebe9f3e1938c55
>> Author: Matthew Wilcox (Oracle) <willy@infradead.org>
>> Date: Mon Aug 14 15:41:00 2023 +0100
>>
>> block: Remove special-casing of compound pages
>
> This looks familiar ... looks like it came up right before Xmas and
> I probably dropped the patch on the floor?
>
> https://lore.kernel.org/all/ZX07SsSqIQ2TYwEi@casper.infradead.org/

Can you send out a proper patch please?

--
Jens Axboe