Messages in this thread Patch in this message | | | From | Wonhyuk Yang <> | Subject | [PATCH] tracing: Fix return value of trace_pid_write() | Date | Tue, 3 May 2022 14:05:46 +0900 |
| |
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
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 Signed-off-by: Wonhyuk Yang <vvghjk1234@gmail.com> --- kernel/trace/trace.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 124f1897fd56..a8bef684e8a3 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; } -- 2.30.2
| |