KASAN: slab-use-after-free Read in jffs2_erase_pending_blocks (2)

Status: upstream: reported on 2026/10/27 01:34
Subsystems: jffs2
Labels: actionable
[Documentation on labels]
Reported-by: syzbot+49c659b5564b2a44083c@syzkaller.appspotmail.com
First crash: 4d14h, last: 3d00h
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
a6ce439c moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Read in jffs2_erase_pending_blocks (2) 2026/10/27 00:00 2026/10/27 00:00 2026/10/27 01:33 168cb7a2
004e4615 repro-c Reproduced: ✅ ❓ KASAN: slab-use-after-free Read in jffs2_erase_pending_blocks (2) 2026/10/25 00:00 2026/10/25 00:00 2026/10/25 02:30 1d9ca40b
b3ecbd9b assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ FuzzingArtifact: ❌ MemoryCorruption: ✅ NetworkNeedsSetup: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in jffs2_erase_pending_blocks (2) 2026/10/24 02:02 2026/10/24 02:02 2026/10/24 03:08 1d9ca40b
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [jffs2?] KASAN: slab-use-after-free Read in jffs2_erase_pending_blocks (2) 0 (1) 2026/10/27 01:34
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in jffs2_erase_pending_blocks jffs2 19 1 932d 931d 0/29 auto-obsoleted due to no activity on 2024/07/16 09:45
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/10/25 02:37 19m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 6fba331225f5040e93d0947d1027e9712238291f report job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in list_empty include/linux/list.h:419 [inline]
BUG: KASAN: slab-use-after-free in jffs2_erase_pending_blocks+0x217/0x2400 fs/jffs2/erase.c:108
Read of size 8 at addr ffff88803c752228 by task jffs2_gcd_mtd0/8922

CPU: 1 UID: 0 PID: 8922 Comm: jffs2_gcd_mtd0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 list_empty include/linux/list.h:419 [inline]
 jffs2_erase_pending_blocks+0x217/0x2400 fs/jffs2/erase.c:108
 jffs2_garbage_collect_pass+0x6cc/0x2170 fs/jffs2/gc.c:253
 jffs2_garbage_collect_thread+0x693/0x720 fs/jffs2/background.c:155
 kthread+0x38b/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 8839:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:409 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x3d0/0x670 mm/slub.c:5563
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 jffs2_init_fs_context+0x4f/0xc0 fs/jffs2/super.c:314
 alloc_fs_context+0x99e/0xd00 fs/fs_context.c:295
 do_new_mount+0x177/0xb00 fs/namespace.c:3966
 do_mount fs/namespace.c:4350 [inline]
 __do_sys_mount fs/namespace.c:4565 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4542
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 7208:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:264 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:296
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2748 [inline]
 slab_free mm/slub.c:6509 [inline]
 kfree+0x1c5/0x6d0 mm/slub.c:6802
 deactivate_locked_super+0xbe/0x110 fs/super.c:586
 cleanup_mnt+0x204/0x2a0 fs/namespace.c:1396
 task_work_run+0x1d9/0x260 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:343 [inline]
 do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88803c752000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 552 bytes inside of
 freed 4096-byte region [ffff88803c752000, ffff88803c753000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3c750
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813ff11140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813ff11140 dead000000000100 dead000000000122
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 0080000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5254, tgid 5254 (dhcpcd), ts 52755560116
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x2591/0x2600 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x230/0x5c0 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3347 [inline]
 allocate_slab+0x7d/0x620 mm/slub.c:3462
 new_slab mm/slub.c:3513 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7418
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x339/0x690 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 __do_kmalloc_node mm/slub.c:5413 [inline]
 __kmalloc_node_track_caller_noprof+0x619/0x7b0 mm/slub.c:5545
 kmalloc_reserve net/core/skbuff.c:638 [inline]
 __alloc_skb+0x2c1/0x7a0 net/core/skbuff.c:716
 alloc_skb include/linux/skbuff.h:1390 [inline]
 nlmsg_new include/net/netlink.h:1055 [inline]
 ctrl_build_family_msg net/netlink/genetlink.c:1387 [inline]
 ctrl_getfamily+0x3d0/0x5c0 net/netlink/genetlink.c:1467
 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114
 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
 genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209
 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2576
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
 netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline]
 netlink_unicast+0x90c/0xac0 net/netlink/af_netlink.c:1361
 netlink_sendmsg+0x7f0/0xb20 net/netlink/af_netlink.c:1920
 sock_sendmsg_nosec+0x14e/0x190 net/socket.c:800
page last free pid 5254 tgid 5254 ts 52751440575 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0xf8e/0x1070 mm/page_alloc.c:2962
 skb_release_all net/core/skbuff.c:1188 [inline]
 __kfree_skb+0x5d/0x210 net/core/skbuff.c:1202
 netlink_recvmsg+0x5ce/0xa70 net/netlink/af_netlink.c:1998
 sock_recvmsg_nosec net/socket.c:1154 [inline]
 sock_recvmsg+0x196/0x1e0 net/socket.c:1176
 ____sys_recvmsg+0x1f6/0x510 net/socket.c:2935
 ___sys_recvmsg+0x213/0x5a0 net/socket.c:2977
 __sys_recvmsg net/socket.c:3010 [inline]
 __do_sys_recvmsg net/socket.c:3016 [inline]
 __se_sys_recvmsg net/socket.c:3013 [inline]
 __x64_sys_recvmsg+0x1b4/0x290 net/socket.c:3013
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88803c752100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803c752180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88803c752200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88803c752280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803c752300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/24 06:17 upstream 734bef548a96 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in jffs2_erase_pending_blocks
2026/10/22 16:16 upstream 7be4bc52fd9e b55fad29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-use-after-free Read in jffs2_erase_pending_blocks
* Struck through repros no longer work on HEAD.