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

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Date: Tue, 16 Jan 2024 11:00:52 -0700
From: Jens Axboe <axboe@...nel.dk>
To: syzbot <syzbot+004c1e0fced2b4bc3dcc@...kaller.appspotmail.com>,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzkaller-bugs@...glegroups.com, Matthew Wilcox <willy@...radead.org>
Subject: Re: [syzbot] [block?] BUG: unable to handle kernel NULL pointer
 dereference in __bio_release_pages

On 1/16/24 2:57 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    052d534373b7 Merge tag 'exfat-for-6.8-rc1' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17957913e80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9603f9823d535d97
> dashboard link: https://syzkaller.appspot.com/bug?extid=004c1e0fced2b4bc3dcc
> compiler:       aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13529733e80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=166850dde80000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/384ffdcca292/non_bootable_disk-052d5343.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/74cc52d4cc15/vmlinux-052d5343.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/a2da7e6a234c/Image-052d5343.gz.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+004c1e0fced2b4bc3dcc@...kaller.appspotmail.com
> 
> Unable to handle kernel paging request at virtual address dfff800000000001
> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> Mem abort info:
>   ESR = 0x0000000096000005
>   EC = 0x25: DABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x05: level 1 translation fault
> Data abort info:
>   ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
>   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
>   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> [dfff800000000001] address between user and kernel address ranges
> Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 1 PID: 3139 Comm: syz-executor303 Not tainted 6.7.0-syzkaller-09928-g052d534373b7 #0
> Hardware name: linux,dummy-virt (DT)
> 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
>  __blkdev_direct_IO block/fops.c:213 [inline]
>  blkdev_direct_IO.part.0+0xf08/0x13c0 block/fops.c:379
>  blkdev_direct_IO block/fops.c:370 [inline]
>  blkdev_direct_write block/fops.c:648 [inline]
>  blkdev_write_iter+0x430/0x91c block/fops.c:706
>  call_write_iter include/linux/fs.h:2085 [inline]
>  do_iter_readv_writev+0x194/0x298 fs/read_write.c:741
>  vfs_writev+0x244/0x684 fs/read_write.c:971
>  do_pwritev+0x15c/0x1e0 fs/read_write.c:1072
>  __do_sys_pwritev2 fs/read_write.c:1131 [inline]
>  __se_sys_pwritev2 fs/read_write.c:1122 [inline]
>  __arm64_sys_pwritev2+0xac/0x120 fs/read_write.c:1122
>  __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
>  invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:51
>  el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:136
>  do_el0_svc+0x40/0x58 arch/arm64/kernel/syscall.c:155
>  el0_svc+0x58/0x140 arch/arm64/kernel/entry-common.c:678
>  el0t_64_sync_handler+0x100/0x12c arch/arm64/kernel/entry-common.c:696
>  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
> Code: d2d00001 f2fbffe1 91002260 d343fc02 (38e16841) 
> ---[ end trace 0000000000000000 ]---
> ----------------
> Code disassembly (best guess):
>    0:	d2d00001 	mov	x1, #0x800000000000        	// #140737488355328
>    4:	f2fbffe1 	movk	x1, #0xdfff, lsl #48
>    8:	91002260 	add	x0, x19, #0x8
>    c:	d343fc02 	lsr	x2, x0, #3
> * 10:	38e16841 	ldrsb	w1, [x2, x1] <-- trapping instruction

This looks to be caused by:

commit 1b151e2435fc3a9b10c8946c6aebe9f3e1938c55
Author: Matthew Wilcox (Oracle) <willy@...radead.org>
Date:   Mon Aug 14 15:41:00 2023 +0100

    block: Remove special-casing of compound pages

-- 
Jens Axboe