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

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Message-ID: <680e57ca.050a0220.2b69d1.00e3.GAE@google.com>
Date: Sun, 27 Apr 2025 09:14:02 -0700
From: syzbot <syzbot+3291296495fc970e4b1c@...kaller.appspotmail.com>
To: axboe@...nel.dk, contact@...aud-lcm.com, linux-block@...r.kernel.org, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [block?] BUG: unable to handle kernel NULL pointer
 dereference in guard_bio_eod

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
BUG: unable to handle kernel NULL pointer dereference in submit_bio_noacct

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000018
Mem abort info:
  ESR = 0x0000000096000006
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x06: level 2 translation fault
Data abort info:
  ISV = 0,
  ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000
  CM = 0, WnR = 0, TnD = 0, TagAccess = 0
  GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 52-bit VAs, pgdp=000000004592d480
[0000000000000018] pgd=0800000046c2f403, p4d=0800000052289403, pud=080000005227c403, pmd=0000000000000000
Internal error: Oops: 0000000096000006 [#1]  SMP
Modules linked in:
CPU: 0 UID: 0 PID: 3990 Comm: syz.1.17 Not tainted 6.15.0-rc3-syzkaller-g5bc1018675ec-dirty #0 PREEMPT 
Hardware name: linux,dummy-virt (DT)
pstate: 41402009 (nZcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
pc : bdev_get_queue include/linux/blkdev.h:951 [inline]
pc : submit_bio_noacct+0x20/0x500 block/blk-core.c:780
lr : submit_bio+0xa8/0x1e0 block/blk-core.c:916
sp : ffff80008975b8a0
x29: ffff80008975b8a0 x28: f8f0000003f32000 x27: ffff80008975b9e0
x26: 0000000000000000 x25: ffff80008975b9c0 x24: 0000000000000000
x23: 0000000000000000 x22: 0000000000000000 x21: ffffc1ffc044c900
x20: 0000000000000000 x19: f8f0000003f32000 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
x14: ffffc1ffc044c900 x13: 0000000000000000 x12: f8f0000003f32000
x11: 0000000000000000 x10: fff000007f9ff330 x9 : 0000000000000002
x8 : 00000000000000b0 x7 : f7f000000446467c x6 : f7f00000032e0c00
x5 : f7f00000032e0c00 x4 : 0000000000000000 x3 : 0000000000000000
x2 : 0000000000000078 x1 : 0000000000000000 x0 : 0000000000080000
Call trace:
 submit_bio_noacct+0x20/0x500 block/blk-core.c:789 (P)
 submit_bio+0xa8/0x1e0 block/blk-core.c:916
 mpage_bio_submit_read fs/mpage.c:75 [inline]
 do_mpage_readpage+0x2d8/0x6dc fs/mpage.c:296
 mpage_readahead+0xcc/0x164 fs/mpage.c:371
 blkdev_readahead+0x18/0x24 block/fops.c:472
 read_pages+0x70/0x2b8 mm/readahead.c:160
 page_cache_ra_order+0x238/0x400 mm/readahead.c:515
 do_sync_mmap_readahead mm/filemap.c:3262 [inline]
 filemap_fault+0x444/0x924 mm/filemap.c:3403
 __do_fault+0x3c/0x21c mm/memory.c:5098
 do_shared_fault mm/memory.c:5582 [inline]
 do_fault mm/memory.c:5656 [inline]
 do_pte_missing mm/memory.c:4160 [inline]
 handle_pte_fault mm/memory.c:5997 [inline]
 __handle_mm_fault+0xadc/0x1b00 mm/memory.c:6140
 handle_mm_fault+0x164/0x314 mm/memory.c:6309
 do_page_fault+0x118/0x688 arch/arm64/mm/fault.c:647
 do_translation_fault+0xac/0xbc arch/arm64/mm/fault.c:783
 do_mem_abort+0x44/0x94 arch/arm64/mm/fault.c:919
 el0_da+0x78/0xa8 arch/arm64/kernel/entry-common.c:604
 el0t_64_sync_handler+0xc4/0x138 arch/arm64/kernel/entry-common.c:765
 el0t_64_sync+0x1a4/0x1a8 arch/arm64/kernel/entry.S:600
Code: aa0003f3 a9025bf5 f9400414 b9401000 (f9400e96) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	aa0003f3 	mov	x19, x0
   4:	a9025bf5 	stp	x21, x22, [sp, #32]
   8:	f9400414 	ldr	x20, [x0, #8]
   c:	b9401000 	ldr	w0, [x0, #16]
* 10:	f9400e96 	ldr	x22, [x20, #24] <-- trapping instruction


Tested on:

commit:         5bc10186 Merge tag 'pci-v6.15-fixes-3' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11cd2374580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=eb8161d1e10a2d09
dashboard link: https://syzkaller.appspot.com/bug?extid=3291296495fc970e4b1c
compiler:       aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1625a368580000