[syzbot] [mm?] [ext4?] BUG: unable to handle kernel NULL pointer dereference in qlist_free_all (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: df685633c3db Merge tag 'rcu-fixes.v7.1-20260519a' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17beec2e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d0f0911eedbc130a
dashboard link: https://syzkaller.appspot.com/bug?extid=741fee3eb7f4c4e6992a
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=110e6b06580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=146b4c2e580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/90074e46cb62/disk-df685633.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/691247547753/vmlinux-df685633.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e1c705a2acac/bzImage-df685633.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+741fee...@syzkaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000008
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 800000007c8b6067 P4D 800000007c8b6067 PUD 0
Oops: Oops: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 7032 Comm: syz.0.224 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:qlink_to_cache mm/kasan/quarantine.c:131 [inline]
RIP: 0010:qlist_free_all+0x8d/0xf0 mm/kasan/quarantine.c:176
Code: 48 89 c2 48 c1 e2 06 48 03 15 1f 8a a7 0b 48 8b 42 08 48 89 c1 83 e1 01 48 83 e9 01 48 09 c8 48 21 d0 80 78 33 f5 49 0f 45 c5 <48> 8b 68 08 eb 88 48 83 7d 40 00 75 9b 66 f7 45 08 04 02 75 93 8b
RSP: 0018:ffffc9000654f428 EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffff88802c2a8000 RCX: ffffffffffffffff
RDX: ffffea0000b0aa00 RSI: ffffffff8df1f2e9 RDI: ffff88802c2a8000
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88802c2a8000
R13: 0000000000000000 R14: ffffc9000654f458 R15: 0000000000000100
FS: 00007fa39d6a46c0(0000) GS:ffff888124374000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 00000000757fe000 CR4: 00000000003526f0
Call Trace:
<TASK>
kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4569 [inline]
slab_alloc_node mm/slub.c:4898 [inline]
kmem_cache_alloc_noprof+0x241/0x6e0 mm/slub.c:4905
vm_area_alloc+0x1f/0x160 mm/vma_init.c:32
__mmap_new_vma mm/vma.c:2547 [inline]
__mmap_region+0x104d/0x2da0 mm/vma.c:2771
mmap_region+0x35d/0x620 mm/vma.c:2857
do_mmap+0xc63/0x12f0 mm/mmap.c:560
vm_mmap_pgoff+0x29e/0x470 mm/util.c:581
ksys_mmap_pgoff+0xe4/0x610 mm/mmap.c:606
__do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline]
__se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline]
__x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa39c79ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa39d6a4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007fa39ca15fa0 RCX: 00007fa39c79ce59
RDX: 00000000000000db RSI: 0000000004020009 RDI: 0000000000000000
RBP: 00007fa39c832d6f R08: 0000000000000401 R09: 0000000000008000
R10: 0000000000000eb1 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa39ca16038 R14: 00007fa39ca15fa0 R15: 00007fffb789fb58
</TASK>
Modules linked in:
CR2: 0000000000000008
---[ end trace 0000000000000000 ]---
RIP: 0010:qlink_to_cache mm/kasan/quarantine.c:131 [inline]
RIP: 0010:qlist_free_all+0x8d/0xf0 mm/kasan/quarantine.c:176
Code: 48 89 c2 48 c1 e2 06 48 03 15 1f 8a a7 0b 48 8b 42 08 48 89 c1 83 e1 01 48 83 e9 01 48 09 c8 48 21 d0 80 78 33 f5 49 0f 45 c5 <48> 8b 68 08 eb 88 48 83 7d 40 00 75 9b 66 f7 45 08 04 02 75 93 8b
RSP: 0018:ffffc9000654f428 EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffff88802c2a8000 RCX: ffffffffffffffff
RDX: ffffea0000b0aa00 RSI: ffffffff8df1f2e9 RDI: ffff88802c2a8000
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88802c2a8000
R13: 0000000000000000 R14: ffffc9000654f458 R15: 0000000000000100
FS: 00007fa39d6a46c0(0000) GS:ffff888124374000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 00000000757fe000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 48 89 c2 mov %rax,%rdx
3: 48 c1 e2 06 shl $0x6,%rdx
7: 48 03 15 1f 8a a7 0b add 0xba78a1f(%rip),%rdx # 0xba78a2d
e: 48 8b 42 08 mov 0x8(%rdx),%rax
12: 48 89 c1 mov %rax,%rcx
15: 83 e1 01 and $0x1,%ecx
18: 48 83 e9 01 sub $0x1,%rcx
1c: 48 09 c8 or %rcx,%rax
1f: 48 21 d0 and %rdx,%rax
22: 80 78 33 f5 cmpb $0xf5,0x33(%rax)
26: 49 0f 45 c5 cmovne %r13,%rax
* 2a: 48 8b 68 08 mov 0x8(%rax),%rbp <-- trapping instruction
2e: eb 88 jmp 0xffffffb8
30: 48 83 7d 40 00 cmpq $0x0,0x40(%rbp)
35: 75 9b jne 0xffffffd2
37: 66 f7 45 08 04 02 testw $0x204,0x8(%rbp)
3d: 75 93 jne 0xffffffd2
3f: 8b .byte 0x8b


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