syzbot


KASAN: slab-use-after-free Write in gfs2_qd_dealloc

Status: upstream: reported C repro on 2025/07/29 13:42
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+469b584076b88cbb037d@syzkaller.appspotmail.com
First crash: 31d, last: 27d
Fix commit to backport (bisect log) :
tree: upstream
commit 557c024ca7250bb65ae60f16c02074106c2f197b
Author: Andrew Price <anprice@redhat.com>
Date: Wed Jul 16 13:12:07 2025 +0000

  gfs2: Validate i_depth for exhash directories

  
Bug presence (2)
Date Name Commit Repro Result
2025/08/02 linux-6.6.y (ToT) 3a8ababb8b6a C [report] KASAN: slab-use-after-free Write in gfs2_qd_dealloc
2025/08/02 upstream (ToT) a6923c06a3b2 C Didn't crash
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Write in gfs2_qd_dealloc (2) gfs2 24 syz 1 515d 515d 0/29 auto-obsoleted due to no activity on 2024/07/09 22:19
upstream KASAN: slab-use-after-free Write in gfs2_qd_dealloc gfs2 24 C inconclusive 27 647d 700d 25/29 fixed on 2023/12/21 03:45
upstream KASAN: slab-use-after-free Write in gfs2_qd_dealloc (3) gfs2 24 C 17 13d 93d 0/29 upstream: reported C repro on 2025/05/28 10:08
Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/08/11 03:29 6h33m fix candidate upstream OK (1) job log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1375 [inline]
BUG: KASAN: slab-use-after-free in gfs2_qd_dealloc+0x81/0xe0 fs/gfs2/quota.c:112
Write of size 4 at addr ffff88801dfb8a78 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.6.100-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <IRQ>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x200 mm/kasan/report.c:466
 kasan_report+0x117/0x150 mm/kasan/report.c:579
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x288/0x290 mm/kasan/generic.c:187
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1375 [inline]
 gfs2_qd_dealloc+0x81/0xe0 fs/gfs2/quota.c:112
 rcu_do_batch kernel/rcu/tree.c:2194 [inline]
 rcu_core+0xcc4/0x1720 kernel/rcu/tree.c:2467
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:148
Code: cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d e3 16 3b 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 66 0f 1f 00 55 41 57 41 56
RSP: 0018:ffffc90000187de0 EFLAGS: 000002c6
RAX: e3d2cf38db4d7800 RBX: ffffffff81619a5b RCX: e3d2cf38db4d7800
RDX: 0000000000000001 RSI: ffffffff8aaaba40 RDI: ffffffff8afc6700
RBP: ffffc90000187f20 R08: ffff8880b8f36d4b R09: 1ffff110171e6da9
R10: dffffc0000000000 R11: ffffed10171e6daa R12: ffffffff8e4a7da8
R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff110037ca780
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:170 [inline]
 do_idle+0x1eb/0x510 kernel/sched/idle.c:282
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
 start_secondary+0xee/0xf0 arch/x86/kernel/smpboot.c:323
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>

Allocated by task 5944:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 init_sbd fs/gfs2/ops_fstype.c:77 [inline]
 gfs2_fill_super+0x11b/0x1f80 fs/gfs2/ops_fstype.c:1162
 get_tree_bdev+0x3e4/0x510 fs/super.c:1591
 gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1344
 vfs_get_tree+0x8c/0x280 fs/super.c:1764
 do_new_mount+0x24b/0xa40 fs/namespace.c:3371
 do_mount fs/namespace.c:3711 [inline]
 __do_sys_mount fs/namespace.c:3920 [inline]
 __se_sys_mount+0x2da/0x3c0 fs/namespace.c:3897
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 5944:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1806 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1832
 slab_free mm/slub.c:3816 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3829
 free_sbd fs/gfs2/ops_fstype.c:69 [inline]
 gfs2_fill_super+0x13c7/0x1f80 fs/gfs2/ops_fstype.c:1327
 get_tree_bdev+0x3e4/0x510 fs/super.c:1591
 gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1344
 vfs_get_tree+0x8c/0x280 fs/super.c:1764
 do_new_mount+0x24b/0xa40 fs/namespace.c:3371
 do_mount fs/namespace.c:3711 [inline]
 __do_sys_mount fs/namespace.c:3920 [inline]
 __se_sys_mount+0x2da/0x3c0 fs/namespace.c:3897
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88801dfb8000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 2680 bytes inside of
 freed 8192-byte region [ffff88801dfb8000, ffff88801dfba000)

The buggy address belongs to the physical page:
page:ffffea000077ee00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1dfb8
head:ffffea000077ee00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017842280 ffffea000098c600 0000000000000002
raw: 0000000000000000 0000000080020002 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5626, tgid 5626 (dhcpcd-run-hook), ts 48591777512, free_ts 48591073318
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 alloc_slab_page+0x5d/0x170 mm/slub.c:1876
 allocate_slab mm/slub.c:2023 [inline]
 new_slab+0x87/0x2e0 mm/slub.c:2076
 ___slab_alloc+0xc6d/0x12f0 mm/slub.c:3230
 __slab_alloc mm/slub.c:3329 [inline]
 __slab_alloc_node mm/slub.c:3382 [inline]
 slab_alloc_node mm/slub.c:3475 [inline]
 __kmem_cache_alloc_node+0x1a2/0x260 mm/slub.c:3524
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
 tomoyo_init_log+0x1104/0x1f10 security/tomoyo/audit.c:264
 tomoyo_supervisor+0x32d/0x1080 security/tomoyo/common.c:2089
 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
 tomoyo_env_perm+0x14a/0x1e0 security/tomoyo/environ.c:63
 tomoyo_environ security/tomoyo/domain.c:672 [inline]
 tomoyo_find_next_domain+0x1594/0x1a60 security/tomoyo/domain.c:881
 tomoyo_bprm_check_security+0x116/0x170 security/tomoyo/tomoyo.c:101
 security_bprm_check+0x62/0xa0 security/security.c:1103
 search_binary_handler fs/exec.c:1763 [inline]
 exec_binprm fs/exec.c:1817 [inline]
 bprm_execve+0xa51/0x16f0 fs/exec.c:1892
 do_execveat_common+0x51b/0x6c0 fs/exec.c:1998
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 discard_slab mm/slub.c:2122 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2662
 put_cpu_partial+0x17c/0x250 mm/slub.c:2738
 __slab_free+0x31d/0x410 mm/slub.c:3686
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x13e/0x260 mm/slub.c:3524
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
 tomoyo_init_log+0x1104/0x1f10 security/tomoyo/audit.c:264
 tomoyo_supervisor+0x32d/0x1080 security/tomoyo/common.c:2089
 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
 tomoyo_env_perm+0x14a/0x1e0 security/tomoyo/environ.c:63
 tomoyo_environ security/tomoyo/domain.c:672 [inline]
 tomoyo_find_next_domain+0x1594/0x1a60 security/tomoyo/domain.c:881
 tomoyo_bprm_check_security+0x116/0x170 security/tomoyo/tomoyo.c:101

Memory state around the buggy address:
 ffff88801dfb8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801dfb8980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88801dfb8a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff88801dfb8a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801dfb8b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
----------------
Code disassembly (best guess):
   0:	cc                   	int3
   1:	cc                   	int3
   2:	cc                   	int3
   3:	cc                   	int3
   4:	cc                   	int3
   5:	cc                   	int3
   6:	cc                   	int3
   7:	f3 0f 1e fa          	endbr64
   b:	0f 0b                	ud2
   d:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
  14:	00 00 00
  17:	f3 0f 1e fa          	endbr64
  1b:	66 90                	xchg   %ax,%ax
  1d:	0f 00 2d e3 16 3b 00 	verw   0x3b16e3(%rip)        # 0x3b1707
  24:	f3 0f 1e fa          	endbr64
  28:	fb                   	sti
  29:	f4                   	hlt
* 2a:	c3                   	ret <-- trapping instruction
  2b:	cc                   	int3
  2c:	cc                   	int3
  2d:	cc                   	int3
  2e:	cc                   	int3
  2f:	cc                   	int3
  30:	cc                   	int3
  31:	cc                   	int3
  32:	cc                   	int3
  33:	cc                   	int3
  34:	cc                   	int3
  35:	cc                   	int3
  36:	cc                   	int3
  37:	66 0f 1f 00          	nopw   (%rax)
  3b:	55                   	push   %rbp
  3c:	41 57                	push   %r15
  3e:	41 56                	push   %r14

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/29 16:25 linux-6.6.y dbcb8d8e4163 c4a95487 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-6-kasan KASAN: slab-use-after-free Write in gfs2_qd_dealloc
2025/07/29 13:42 linux-6.6.y dbcb8d8e4163 c4a95487 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Write in gfs2_qd_dealloc
2025/07/29 13:42 linux-6.6.y dbcb8d8e4163 c4a95487 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Write in gfs2_qd_dealloc
2025/07/29 13:41 linux-6.6.y dbcb8d8e4163 c4a95487 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Write in gfs2_qd_dealloc
* Struck through repros no longer work on HEAD.