KASAN: slab-out-of-bounds Read in seq_buf_putmem

Status: upstream: reported on 2026/08/23 13:33
Subsystems: block trace
Labels: prio:normal
[Documentation on labels]
Reported-by: syzbot+f179b16e13624138b0f1@syzkaller.appspotmail.com
First crash: 10d, last: 3d13h
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ID Workflow Result Correct Bug Created Started Finished Revision
5553e0ea assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-out-of-bounds Read in seq_buf_putmem 2026/08/21 01:00 2026/08/21 01:00 2026/08/21 01:57 1e72964b
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[syzbot] [block?] [trace?] KASAN: slab-out-of-bounds Read in seq_buf_putmem 0 (1) 2026/08/23 13:33

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in seq_buf_putmem+0xc9/0x180 lib/seq_buf.c:241
Read of size 7040 at addr ffff888029b88140 by task syz.3.1565/12920

CPU: 0 UID: 0 PID: 12920 Comm: syz.3.1565 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:186 [inline]
 kasan_check_range+0x10f/0x1e0 mm/kasan/generic.c:200
 __asan_memcpy+0x23/0x60 mm/kasan/shadow.c:105
 seq_buf_putmem+0xc9/0x180 lib/seq_buf.c:241
 trace_seq_putmem kernel/trace/trace_seq.c:296 [inline]
 trace_seq_putmem+0x11e/0x230 kernel/trace/trace_seq.c:284
 blk_trace_synthesize_old_trace kernel/trace/blktrace.c:1780 [inline]
 blk_trace_event_print_binary+0x13f/0x1b0 kernel/trace/blktrace.c:1788
 print_bin_fmt kernel/trace/trace.c:3152 [inline]
 print_trace_line+0xc9a/0x1790 kernel/trace/trace.c:3229
 tracing_read_pipe+0x586/0xd60 kernel/trace/trace.c:5446
 vfs_read+0x1e4/0xb40 fs/read_write.c:572
 ksys_read+0x12a/0x250 fs/read_write.c:716
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f09c8d9e0d9
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:00007f09c9c03028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f09c9026090 RCX: 00007f09c8d9e0d9
RDX: 0000000000002028 RSI: 0000200000004500 RDI: 0000000000000007
RBP: 00007f09c8e35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f09c9026128 R14: 00007f09c9026090 R15: 00007fff55f683d8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x29b88
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x44dc0(GFP_KERNEL|__GFP_ZERO|__GFP_RETRY_MAYFAIL|__GFP_COMP), pid 6461, tgid 6455 (syz.0.155), ts 154599399695
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x110d/0x35b0 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
 __alloc_pages_noprof mm/page_alloc.c:5471 [inline]
 alloc_pages_node_noprof+0x93/0x200 mm/page_alloc.c:5485
 alloc_cpu_data+0x20/0x120 kernel/trace/ring_buffer.c:438
 __rb_allocate_pages+0xb38/0xfc0 kernel/trace/ring_buffer.c:2496
 ring_buffer_resize+0x71c/0x1ed0 kernel/trace/ring_buffer.c:3327
 __tracing_resize_ring_buffer.part.0+0x52/0x1f0 kernel/trace/trace.c:4740
 __tracing_resize_ring_buffer kernel/trace/trace.c:4734 [inline]
 tracing_update_buffers+0xd4/0xf0 kernel/trace/trace.c:4979
 ftrace_event_write+0x14a/0x2c0 kernel/trace/trace_events.c:1560
 vfs_write+0x2aa/0x1050 fs/read_write.c:685
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5824 tgid 5824 ts 148836779258 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0x79f/0x10f0 mm/page_alloc.c:2962
 kasan_depopulate_vmalloc_pte+0x5d/0x80 mm/kasan/shadow.c:484
 apply_to_pte_range mm/memory.c:3408 [inline]
 apply_to_pmd_range mm/memory.c:3452 [inline]
 apply_to_pud_range mm/memory.c:3488 [inline]
 apply_to_p4d_range mm/memory.c:3524 [inline]
 __apply_to_page_range+0xb1d/0x1520 mm/memory.c:3560
 __kasan_release_vmalloc+0xd7/0xe0 mm/kasan/shadow.c:602
 kasan_release_vmalloc include/linux/kasan.h:593 [inline]
 kasan_release_vmalloc_node mm/vmalloc.c:2307 [inline]
 purge_vmap_node+0x210/0xb40 mm/vmalloc.c:2329
 __purge_vmap_area_lazy+0x90a/0xc00 mm/vmalloc.c:2419
 drain_vmap_area_work+0x27/0x40 mm/vmalloc.c:2453
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3387
 process_scheduled_works kernel/workqueue.c:3470 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3551
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff888029b88f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888029b89000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888029b89080: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc 00 00
                                     ^
 ffff888029b89100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888029b89180: 00 00 00 00 fc fc fc fc fc fc fc fc 00 00 00 00
==================================================================

Crashes (13):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/26 22:35 upstream 502d45774af0 a2b77b9e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-out-of-bounds Read in seq_buf_putmem
2026/08/20 17:12 upstream a4ff2be345d0 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-out-of-bounds Read in seq_buf_putmem
2026/08/20 17:11 upstream a4ff2be345d0 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-out-of-bounds Read in seq_buf_putmem
2026/08/19 19:20 upstream bd5f485f3f02 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-out-of-bounds Read in seq_buf_putmem
2026/08/19 19:17 upstream bd5f485f3f02 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-out-of-bounds Read in seq_buf_putmem
2026/08/19 19:16 upstream bd5f485f3f02 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-out-of-bounds Read in seq_buf_putmem
2026/08/19 18:50 upstream bd5f485f3f02 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-out-of-bounds Read in seq_buf_putmem
2026/08/19 13:27 upstream bd5f485f3f02 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-out-of-bounds Read in seq_buf_putmem
2026/08/19 17:09 linux-next 6a746cd265ae 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root KASAN: slab-out-of-bounds Read in seq_buf_putmem
2026/08/24 09:06 upstream 4352b8aee980 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-use-after-free Read in seq_buf_putmem
2026/08/20 17:17 upstream a4ff2be345d0 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-use-after-free Read in seq_buf_putmem
2026/08/19 19:12 upstream bd5f485f3f02 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: use-after-free Read in seq_buf_putmem
2026/08/26 08:34 upstream 73ae59e97596 6a91adb4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: use-after-free Read in seq_buf_putmem
* Struck through repros no longer work on HEAD.