UBSAN: array-index-out-of-bounds in trace_ctxwake

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-5.15	UBSAN: array-index-out-of-bounds in trace_ctxwake_print	15				1	2d08h	2d08h	0/3	upstream: reported on 2026/10/29 16:24
================================================================================
UBSAN: array-index-out-of-bounds in ./include/linux/sched.h:1679:9
index 255 is out of range for type 'const char[10]'
CPU: 0 PID: 474 Comm: syz.4.63 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 dump_stack+0x15/0x20 lib/dump_stack.c:113
 ubsan_epilogue+0xe/0x40 lib/ubsan.c:151
 __ubsan_handle_out_of_bounds+0xdf/0xf0 lib/ubsan.c:282
 task_index_to_char include/linux/sched.h:1679 [inline]
 trace_ctxwake_print+0x2ca/0x420 kernel/trace/trace_output.c:944
 trace_ctx_print+0x1c/0x20 kernel/trace/trace_output.c:963
 print_trace_fmt+0x4ed/0x710 kernel/trace/trace.c:4384
 print_trace_line+0x385/0x690 kernel/trace/trace.c:4549
 tracing_read_pipe+0x4fd/0xab0 kernel/trace/trace.c:6825
 vfs_read+0x28c/0xc20 fs/read_write.c:483
 ksys_read+0x14a/0x260 fs/read_write.c:623
 __do_sys_read fs/read_write.c:633 [inline]
 __se_sys_read fs/read_write.c:631 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:631
 x64_sys_call+0x96d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
 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
RIP: 0033:0x7f071bf6ff99
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:00007f071a9c9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f071c1f7fa0 RCX: 00007f071bf6ff99
RDX: 0000000000002000 RSI: 0000200000004000 RDI: 0000000000000009
RBP: 00007f071c006ec4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f071c1f8038 R14: 00007f071c1f7fa0 R15: 00007ffcaa5f5398
 </TASK>
================================================================================
==================================================================
BUG: KASAN: global-out-of-bounds in task_index_to_char include/linux/sched.h:1679 [inline]
BUG: KASAN: global-out-of-bounds in trace_ctxwake_print+0x2e5/0x420 kernel/trace/trace_output.c:944
Read of size 1 at addr ffffffff8546a4bf by task syz.4.63/474

CPU: 0 PID: 474 Comm: syz.4.63 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106