syzbot


KASAN: use-after-free Read in gfs2_quotad

Status: upstream: reported on 2025/06/06 12:35
Reported-by: syzbot+1c60687a1f6580099289@syzkaller.appspotmail.com
First crash: 216d, last: 2d05h
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in gfs2_quotad origin:lts-only 19 C inconclusive 60 8h15m 270d 0/3 upstream: reported C repro on 2025/04/13 18:37
upstream KASAN: slab-use-after-free Read in gfs2_quotad gfs2 19 syz error 4 2d07h 31d 0/29 upstream: reported syz repro on 2025/12/08 08:47

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0xf7/0x7c60 kernel/locking/lockdep.c:4882
Read of size 8 at addr ffff888026f80bb0 by task gfs2_quotad/5582

CPU: 1 PID: 5582 Comm: gfs2_quotad Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 __lock_acquire+0xf7/0x7c60 kernel/locking/lockdep.c:4882
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
 finish_wait+0xb5/0x1d0 kernel/sched/wait.c:407
 gfs2_quotad+0x703/0x880 fs/gfs2/quota.c:1605
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 4249:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc+0xb5/0xf0 mm/kasan/common.c:522
 kmalloc_reserve net/core/skbuff.c:356 [inline]
 __alloc_skb+0x22c/0x750 net/core/skbuff.c:427
 alloc_skb include/linux/skbuff.h:1162 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:664 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:721 [inline]
 nsim_dev_trap_report_work+0x2a1/0xb40 drivers/net/netdevsim/dev.c:762
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Freed by task 4249:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kfree+0xef/0x2a0 mm/slub.c:4564
 skb_free_head net/core/skbuff.c:655 [inline]
 skb_release_data+0x6fe/0x850 net/core/skbuff.c:677
 skb_release_all net/core/skbuff.c:742 [inline]
 __kfree_skb net/core/skbuff.c:756 [inline]
 consume_skb+0xa2/0x100 net/core/skbuff.c:914
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:737 [inline]
 nsim_dev_trap_report_work+0x7cb/0xb40 drivers/net/netdevsim/dev.c:762
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff888026f80000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 2992 bytes inside of
 4096-byte region [ffff888026f80000, ffff888026f81000)
The buggy address belongs to the page:
page:ffffea00009be000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x26f80
head:ffffea00009be000 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888016842140
raw: 0000000000000000 0000000000040004 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 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 4249, ts 148846347422, free_ts 148768553521
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
 __alloc_pages+0x1e1/0x470 mm/page_alloc.c:5487
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x81e/0xdf0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 __kmalloc_node_track_caller+0x1fc/0x3a0 mm/slub.c:4963
 kmalloc_reserve net/core/skbuff.c:356 [inline]
 __alloc_skb+0x22c/0x750 net/core/skbuff.c:427
 alloc_skb include/linux/skbuff.h:1162 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:664 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:721 [inline]
 nsim_dev_trap_report_work+0x2a1/0xb40 drivers/net/netdevsim/dev.c:762
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page+0x94/0x280 mm/page_alloc.c:3396
 free_nonslab_page+0xe2/0x150 mm/slub.c:3540
 kmem_free fs/xfs/kmem.h:62 [inline]
 xlog_dealloc_log+0x172/0x270 fs/xfs/xfs_log.c:2068
 xfs_mountfs+0x1192/0x1b10 fs/xfs/xfs_mount.c:964
 xfs_fs_fill_super+0x11a4/0x13f0 fs/xfs/xfs_super.c:1684
 get_tree_bdev+0x3f1/0x610 fs/super.c:1325
 vfs_get_tree+0x88/0x270 fs/super.c:1530
 do_new_mount+0x24a/0xa40 fs/namespace.c:3034
 do_mount fs/namespace.c:3377 [inline]
 __do_sys_mount fs/namespace.c:3585 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3562
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff888026f80a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888026f80b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888026f80b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff888026f80c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888026f80c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/06 20:08 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in gfs2_quotad
2025/12/08 22:16 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in gfs2_quotad
2025/12/06 10:40 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in gfs2_quotad
2025/11/11 13:26 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in gfs2_quotad
2025/11/06 06:34 linux-5.15.y cc5ec8769306 a6c9c731 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in gfs2_quotad
2025/11/05 18:56 linux-5.15.y cc5ec8769306 a6c9c731 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in gfs2_quotad
2025/10/28 00:17 linux-5.15.y ac56c046adf4 fd2207e7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in gfs2_quotad
2025/06/06 12:35 linux-5.15.y 1c700860e8bc 9fa58bba .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in gfs2_quotad
2025/07/21 09:32 linux-5.15.y c79648372d02 7117feec .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 KASAN: use-after-free Read in gfs2_quotad
2025/12/15 02:22 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in gfs2_quotad
* Struck through repros no longer work on HEAD.