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

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Message-ID: <671bad0e.050a0220.2e773.0006.GAE@google.com>
Date: Fri, 25 Oct 2024 07:37:02 -0700
From: syzbot <syzbot+4089e577072948ac5531@...kaller.appspotmail.com>
To: gianf.trad@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [erofs?] BUG: unable to handle kernel NULL pointer
 dereference in read_cache_folio

Hello,

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

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
Mem abort info:
  ESR = 0x0000000086000006
  EC = 0x21: IABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x06: level 2 translation fault
user pgtable: 4k pages, 52-bit VAs, pgdp=0000000045e33a80
[0000000000000000] pgd=080000004bfb6003, p4d=080000004bd49003, pud=080000004bde6003, pmd=0000000000000000
Internal error: Oops: 0000000086000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 UID: 0 PID: 3935 Comm: syz.0.15 Tainted: G    B              6.12.0-rc4-syzkaller-gae90f6a6170d #0
Tainted: [B]=BAD_PAGE
Hardware name: linux,dummy-virt (DT)
pstate: 61400809 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=-c)
pc : 0x0
lr : filemap_read_folio+0x44/0xf4 mm/filemap.c:2367
sp : ffff8000897b3ac0
x29: ffff8000897b3ac0 x28: fdf0000003bf9180 x27: 0000000020ffd000
x26: 0000000000000000 x25: 0000000000000000 x24: 0000000002100cca
x23: f6f0000003c63780 x22: 0000000000000000 x21: f6f0000003c63780
x20: 0000000000000000 x19: ffffc1ffc0354cc0 x18: ffff8000897b3c20
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000001
x14: 0000000000000000 x13: 0000000000000003 x12: 000000000006b8f7
x11: 0000000000000001 x10: ffff800081f1ae18 x9 : 0000000000000000
x8 : fff07ffffd1ef000 x7 : fff000007f8e9d58 x6 : 0000000000000001
x5 : ffffc1ffc0354cc0 x4 : 0000000000000000 x3 : fbf0000004756d80
x2 : 0000000000000000 x1 : ffffc1ffc0354cc0 x0 : f6f0000003c63780
Call trace:
 0x0
 do_read_cache_folio+0x18c/0x29c mm/filemap.c:3825
 read_cache_folio+0x14/0x20 mm/filemap.c:3857
 freader_get_folio+0x1bc/0x214 lib/buildid.c:77
 freader_fetch+0x44/0x164 lib/buildid.c:120
 __build_id_parse.isra.0+0x98/0x2a8 lib/buildid.c:305
 build_id_parse+0x18/0x24 lib/buildid.c:359
 do_procmap_query+0x670/0x7a0 fs/proc/task_mmu.c:534
 procfs_procmap_ioctl+0x2c/0x44 fs/proc/task_mmu.c:613
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl fs/ioctl.c:893 [inline]
 __arm64_sys_ioctl+0xac/0xf0 fs/ioctl.c:893
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x48/0x110 arch/arm64/kernel/syscall.c:49
 el0_svc_common.constprop.0+0x40/0xe0 arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x1c/0x28 arch/arm64/kernel/syscall.c:151
 el0_svc+0x34/0xec arch/arm64/kernel/entry-common.c:712
 el0t_64_sync_handler+0x100/0x12c arch/arm64/kernel/entry-common.c:730
 el0t_64_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:598
Code: ???????? ???????? ???????? ???????? (????????) 
---[ end trace 0000000000000000 ]---


Tested on:

commit:         ae90f6a6 Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16d3de40580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ed4ea7a5e1330003
dashboard link: https://syzkaller.appspot.com/bug?extid=4089e577072948ac5531
compiler:       aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

Note: no patches were applied.