[v5.15] BUG: unable to handle kernel NULL pointer dereference in lookup_one_unlocked

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fa93fa65db6e Linux 5.15.165
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1697804d980000
kernel config: https://syzkaller.appspot.com/x/.config?x=94fbccfcb9fcb5e2
dashboard link: https://syzkaller.appspot.com/bug?extid=1850d38cdeb50dbd013d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c53aa76a46f7/disk-fa93fa65.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d8a8addbfe73/vmlinux-fa93fa65.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1825ecda41d8/Image-fa93fa65.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1850d3...@syzkaller.appspotmail.com

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, 48-bit VAs, pgdp=00000001255ea000
[0000000000000000] pgd=080000010a919003, p4d=080000010a919003, pud=080000011a8b4003, pmd=0000000000000000
Internal error: Oops: 0000000086000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 5074 Comm: syz.4.221 Not tainted 5.15.165-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : 0x0
lr : __lookup_slow+0x250/0x388 fs/namei.c:1663
sp : ffff80001d4b7500
x29: ffff80001d4b75e0 x28: 0000000010000000 x27: 1fffe0001cb8748d
x26: dfff800000000000 x25: ffff700003a96ea4 x24: ffff80001d4b7540
x23: ffff0000dd5b4018 x22: ffff80001d4b7660 x21: ffff800011cb6280
x20: 0000000000000000 x19: ffff0000e5c3a468 x18: ffff80001d4b7060
x17: 0000000000000002 x16: ffff800011aaffbc x15: 0000000000030c15
x14: 00000000b5a9332d x13: dfff800000000000 x12: 0000000000040000
x11: 0000000000000000 x10: 0000000000000002 x9 : ffff0000c21e3680
x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
x5 : ffff8000179270a0 x4 : 0000000000000000 x3 : ffff8000089e0bd4
x2 : 0000000000000000 x1 : ffff0000e5c3a468 x0 : ffff0000dd5b4018
Call trace:
0x0
lookup_slow fs/namei.c:1680 [inline]
lookup_one_unlocked+0x144/0x254 fs/namei.c:2779
lookup_one_len_unlocked+0x3c/0x50 fs/namei.c:2833
ovl_lookup_positive_unlocked fs/overlayfs/namei.c:205 [inline]
ovl_lookup_single+0x84/0x6c4 fs/overlayfs/namei.c:230
ovl_lookup_layer+0x368/0x454 fs/overlayfs/namei.c:314
ovl_lookup+0x840/0x1928 fs/overlayfs/namei.c:914
lookup_one_qstr_excl+0x108/0x230 fs/namei.c:1563
do_unlinkat+0x2f0/0x830 fs/namei.c:4332
__do_sys_unlinkat fs/namei.c:4391 [inline]
__se_sys_unlinkat fs/namei.c:4384 [inline]
__arm64_sys_unlinkat+0xcc/0xfc fs/namei.c:4384
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
Code: bad PC value
---[ end trace e1fe2be347c9bb6a ]---


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: fa93fa65db6e Linux 5.15.165
git tree: linux-5.15.y

console output: https://syzkaller.appspot.com/x/log.txt?x=1531de33980000

kernel config: https://syzkaller.appspot.com/x/.config?x=94fbccfcb9fcb5e2
dashboard link: https://syzkaller.appspot.com/bug?extid=1850d38cdeb50dbd013d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1394e339980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15dc2925980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c53aa76a46f7/disk-fa93fa65.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d8a8addbfe73/vmlinux-fa93fa65.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1825ecda41d8/Image-fa93fa65.gz.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/e5e79bdbf4f9/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1850d3...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 64
overlayfs: fs on './file0' does not support file handles, falling back to index=off,nfs_export=off.

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, 48-bit VAs, pgdp=000000010a4eb000
[0000000000000000] pgd=080000010a0e3003, p4d=080000010a0e3003, pud=080000010d868003, pmd=0000000000000000

Internal error: Oops: 0000000086000006 [#1] PREEMPT SMP
Modules linked in:

CPU: 1 PID: 4015 Comm: syz-executor206 Not tainted 5.15.165-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : 0x0
lr : __lookup_slow+0x250/0x388 fs/namei.c:1663

sp : ffff800018ff7500
x29: ffff800018ff75e0 x28: 0000000010000000 x27: 1fffe0001b04b3ac
x26: dfff800000000000 x25: ffff7000031feea4 x24: ffff800018ff7540
x23: ffff0000dc2c8018 x22: ffff800018ff7660 x21: ffff800011cb6280
x20: 0000000000000000 x19: ffff0000d8259d60 x18: ffff800018ff7060
x17: 0000000000000000 x16: ffff800011aaffbc x15: 000000000000be2d
x14: 00000000b5a9332d x13: dfff800000000000 x12: 0000000000000001
x11: 0000000000000000 x10: 0000000000000000 x9 : ffff0000c8333680

x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000

x5 : ffff80001777ee20 x4 : 0000000000000000 x3 : ffff8000089e0bd4
x2 : 0000000000000000 x1 : ffff0000d8259d60 x0 : ffff0000dc2c8018

Call trace:
0x0
lookup_slow fs/namei.c:1680 [inline]
lookup_one_unlocked+0x144/0x254 fs/namei.c:2779
lookup_one_len_unlocked+0x3c/0x50 fs/namei.c:2833
ovl_lookup_positive_unlocked fs/overlayfs/namei.c:205 [inline]
ovl_lookup_single+0x84/0x6c4 fs/overlayfs/namei.c:230
ovl_lookup_layer+0x368/0x454 fs/overlayfs/namei.c:314
ovl_lookup+0x840/0x1928 fs/overlayfs/namei.c:914
lookup_one_qstr_excl+0x108/0x230 fs/namei.c:1563
do_unlinkat+0x2f0/0x830 fs/namei.c:4332
__do_sys_unlinkat fs/namei.c:4391 [inline]
__se_sys_unlinkat fs/namei.c:4384 [inline]
__arm64_sys_unlinkat+0xcc/0xfc fs/namei.c:4384
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
Code: bad PC value

---[ end trace b93e3b587ae89b38 ]---


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[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.