On 2025/8/21 15:17, Pu Lehui wrote:
From: Pu Lehui <[email protected]>
When trace_get_user in trace_pid_write parses an only space, the
!trace_parser_loaded branch will break with no errno, causing
tr->filtered_pids to still be assigned with pid_list, which may trigger
potential problems.
Hi Steven,
Sorry, this patch will break the cleanup functionality of
"set_ftrace_pid" as indicated in [0]. Pls ignore this patch.
Link: https://lore.kernel.org/all/[email protected] [0]
This patch will also silence the fault injection syzkaller warning in
tracepoint_add_func [0]. 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.
As for this fault injection syzkaller issue, shall we need to silence
it? How about the below fix?
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e6b50b416e63..c17c031e7917 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -834,7 +834,11 @@ 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) {
+ trace_parser_put(&parser);
+ return ret;
+ }
ret = trace_pid_list_next(filtered_pids, pid +
1, &pid);
nr_pids++;
}
Link: https://lore.kernel.org/all/[email protected]
[0]
Fixes: b27f266f74fb ("tracing: Fix return value of trace_pid_write()")
Signed-off-by: Pu Lehui <[email protected]>
---
kernel/trace/trace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8d8935ed416d..feeb7eb71318 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -853,10 +853,10 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
ubuf += ret;
cnt -= ret;
+ ret = -EINVAL;
if (!trace_parser_loaded(&parser))
break;
- ret = -EINVAL;
if (kstrtoul(parser.buffer, 0, &val))
break;
