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authorWonhyuk Yang2022-05-03 14:05:46 +0900
committerSteven Rostedt (Google)2022-05-26 21:12:59 -0400
commitb27f266f74fbda4ee36c2b2b04d15992860cf23b (patch)
tree3a0899d6324bd9e7a74ad0a0c2be1e17ee300609 /kernel
parent99696a2592bca641eb88cc9a80c90e591afebd0f (diff)
tracing: Fix return value of trace_pid_write()
Setting set_event_pid with trailing whitespace lead to endless write system calls like below. $ strace echo "123 " > /sys/kernel/debug/tracing/set_event_pid execve("/usr/bin/echo", ["echo", "123 "], ...) = 0 ... write(1, "123 \n", 5) = 4 write(1, "\n", 1) = 0 write(1, "\n", 1) = 0 write(1, "\n", 1) = 0 write(1, "\n", 1) = 0 write(1, "\n", 1) = 0 .... This is because, the result of trace_get_user's are not returned when it read at least one pid. To fix it, update read variable even if parser->idx == 0. The result of applied patch is below. $ strace echo "123 " > /sys/kernel/debug/tracing/set_event_pid execve("/usr/bin/echo", ["echo", "123 "], ...) = 0 ... write(1, "123 \n", 5) = 5 close(1) = 0 Link: https://lkml.kernel.org/r/20220503050546.288911-1-vvghjk1234@gmail.com Cc: Ingo Molnar <mingo@redhat.com> Cc: Baik Song An <bsahn@etri.re.kr> Cc: Hong Yeon Kim <kimhy@etri.re.kr> Cc: Taeung Song <taeung@reallinux.co.kr> Cc: linuxgeek@linuxgeek.io Cc: stable@vger.kernel.org Fixes: 4909010788640 ("tracing: Add set_event_pid directory for future use") Signed-off-by: Wonhyuk Yang <vvghjk1234@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 498ae22d4ffa..4825883b2ffd 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -721,13 +721,16 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
pos = 0;
ret = trace_get_user(&parser, ubuf, cnt, &pos);
- if (ret < 0 || !trace_parser_loaded(&parser))
+ if (ret < 0)
break;
read += ret;
ubuf += ret;
cnt -= ret;
+ if (!trace_parser_loaded(&parser))
+ break;
+
ret = -EINVAL;
if (kstrtoul(parser.buffer, 0, &val))
break;
@@ -753,7 +756,6 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
if (!nr_pids) {
/* Cleared the list of pids */
trace_pid_list_free(pid_list);
- read = ret;
pid_list = NULL;
}