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: 6d10h, last: 1d14h
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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+0x124/0x180 lib/seq_buf.c:241
Read of size 1352 at addr ffff8880295bdb98 by task syz.2.2551/19243

CPU: 1 UID: 0 PID: 19243 Comm: syz.2.2551 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
 seq_buf_putmem+0x124/0x180 lib/seq_buf.c:241
 blk_trace_synthesize_old_trace kernel/trace/blktrace.c:1780 [inline]
 blk_trace_event_print_binary+0x130/0x1b0 kernel/trace/blktrace.c:1788
 tracing_read_pipe+0x568/0xb50 kernel/trace/trace.c:5444
 vfs_read+0x213/0xa80 fs/read_write.c:572
 ksys_read+0x150/0x270 fs/read_write.c:716
 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
RIP: 0033:0x7f32fcb9e0d9
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:00007f32fd9ac028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f32fce25fa0 RCX: 00007f32fcb9e0d9
RDX: 00000000fffffe23 RSI: 0000200000001500 RDI: 0000000000000003
RBP: 00007f32fcc35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f32fce26038 R14: 00007f32fce25fa0 R15: 00007ffe116411a8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880295bd000 pfn:0x295bd
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: ffff8880295bd000 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 16263, tgid 16262 (syz.4.1733), ts 1361028187121, free_ts 1361025032368
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0x21fe/0x2270 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 __alloc_pages_noprof+0x10/0x100 mm/page_alloc.c:5338
 __alloc_pages_node_noprof include/linux/gfp.h:291 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:318 [inline]
 alloc_cpu_data kernel/trace/ring_buffer.c:438 [inline]
 __rb_allocate_pages+0xe97/0x17f0 kernel/trace/ring_buffer.c:2496
 ring_buffer_resize+0x51d/0x1670 kernel/trace/ring_buffer.c:3327
 __tracing_resize_ring_buffer+0x9c/0x310 kernel/trace/trace.c:4738
 tracing_set_tracer+0x83/0x790 kernel/trace/trace.c:5014
 tracing_set_trace_write+0x147/0x210 kernel/trace/trace.c:5131
 vfs_write+0x296/0xba0 fs/read_write.c:685
 ksys_write+0x150/0x270 fs/read_write.c:739
 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
page last free pid 23 tgid 23 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0xc22/0xd20 mm/page_alloc.c:2950
 __tlb_remove_table_free mm/mmu_gather.c:228 [inline]
 tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:291
 rcu_do_batch kernel/rcu/tree.c:2645 [inline]
 rcu_core+0x794/0x10b0 kernel/rcu/tree.c:2897
 handle_softirqs+0x226/0x860 kernel/softirq.c:645
 run_ksoftirqd+0x36/0x60 kernel/softirq.c:1108
 smpboot_thread_fn+0x565/0xa70 kernel/smpboot.c:160
 kthread+0x38b/0x480 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

Memory state around the buggy address:
 ffff8880295bdf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880295be000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880295be080: 00 00 00 00 00 00 00 00 01 fc fc fc fc fc fc fc
                                           ^
 ffff8880295be100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880295be180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
* Struck through repros no longer work on HEAD.