On Mon, 8 Sep 2025 02:46:58 +0000 Pu Lehui <[email protected]> wrote:
> From: Pu Lehui <[email protected]> > > Syzkaller trigger a fault injection warning: > > WARNING: CPU: 1 PID: 12326 at tracepoint_add_func+0xbfc/0xeb0 > Modules linked in: > CPU: 1 UID: 0 PID: 12326 Comm: syz.6.10325 Tainted: G U 6.14.0-rc5-syzkaller > #0 > Tainted: [U]=USER > Hardware name: Google Compute Engine/Google Compute Engine > RIP: 0010:tracepoint_add_func+0xbfc/0xeb0 kernel/tracepoint.c:294 > Code: 09 fe ff 90 0f 0b 90 0f b6 74 24 43 31 ff 41 bc ea ff ff ff > RSP: 0018:ffffc9000414fb48 EFLAGS: 00010283 > RAX: 00000000000012a1 RBX: ffffffff8e240ae0 RCX: ffffc90014b78000 > RDX: 0000000000080000 RSI: ffffffff81bbd78b RDI: 0000000000000001 > RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 > R10: 0000000000000001 R11: 0000000000000001 R12: ffffffffffffffef > R13: 0000000000000000 R14: dffffc0000000000 R15: ffffffff81c264f0 > FS: 00007f27217f66c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000001b2e80dff8 CR3: 00000000268f8000 CR4: 00000000003526f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <TASK> > tracepoint_probe_register_prio+0xc0/0x110 kernel/tracepoint.c:464 > register_trace_prio_sched_switch include/trace/events/sched.h:222 [inline] > register_pid_events kernel/trace/trace_events.c:2354 [inline] > event_pid_write.isra.0+0x439/0x7a0 kernel/trace/trace_events.c:2425 > vfs_write+0x24c/0x1150 fs/read_write.c:677 > ksys_write+0x12b/0x250 fs/read_write.c:731 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > We can reproduce the warning by following the steps below: > 1. echo 8 >> set_event_notrace_pid. Let tr->filtered_pids owns one pid > and register sched_switch tracepoint. > 2. echo ' ' >> set_event_pid, and perform fault injection during chunk > allocation of trace_pid_list_alloc. Let pid_list with no pid and > assign to tr->filtered_pids. > 3. echo ' ' >> set_event_pid. Let pid_list is NULL and assign to > tr->filtered_pids. > 4. echo 9 >> set_event_pid, will trigger the double register > sched_switch tracepoint warning. > > The reason is that syzkaller injects a fault into the chunk allocation > in trace_pid_list_alloc, causing a failure in trace_pid_list_set, which > may trigger double register of the same tracepoint. This only occurs > when the system is about to crash, but to suppress this warning, let's > add failure handling logic to trace_pid_list_set. > > Fixes: 8d6e90983ade ("tracing: Create a sparse bitmask for pid filtering") > Reported-by: [email protected] > Closes: > https://lore.kernel.org/all/[email protected] > Signed-off-by: Pu Lehui <[email protected]> Looks good to me. Reviewed-by: Masami Hiramatsu (Google) <[email protected]> Thank you, > --- > kernel/trace/trace.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 1b7db732c0b1..f2a84d1ce4b7 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -834,7 +834,10 @@ int trace_pid_write(struct trace_pid_list *filtered_pids, > /* copy the current bits to the new max */ > ret = trace_pid_list_first(filtered_pids, &pid); > while (!ret) { > - trace_pid_list_set(pid_list, pid); > + ret = trace_pid_list_set(pid_list, pid); > + if (ret < 0) > + goto out; > + > ret = trace_pid_list_next(filtered_pids, pid + 1, &pid); > nr_pids++; > } > @@ -871,6 +874,7 @@ int trace_pid_write(struct trace_pid_list *filtered_pids, > trace_parser_clear(&parser); > ret = 0; > } > + out: > trace_parser_put(&parser); > > if (ret < 0) { > -- > 2.34.1 > -- Masami Hiramatsu (Google) <[email protected]>
