diff options
| author | Vasily Averin <vvs@virtuozzo.com> | 2020-01-24 10:02:56 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-02-28 15:42:40 +0100 |
| commit | b4b5af0b31e6b7cb85989d076824bf4590655c34 (patch) | |
| tree | e3739fa5946e401352d4dc4a23879fa52e1f6b3a /kernel | |
| parent | 25b357f1f82a5d2c061f5fb3e6110572f2285036 (diff) | |
ftrace: fpid_next() should increase position index
[ Upstream commit e4075e8bdffd93a9b6d6e1d52fabedceeca5a91b ]
if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.
Without patch:
# dd bs=4 skip=1 if=/sys/kernel/tracing/set_ftrace_pid
dd: /sys/kernel/tracing/set_ftrace_pid: cannot skip to specified offset
id
no pid
2+1 records in
2+1 records out
10 bytes copied, 0.000213285 s, 46.9 kB/s
Notice the "id" followed by "no pid".
With the patch:
# dd bs=4 skip=1 if=/sys/kernel/tracing/set_ftrace_pid
dd: /sys/kernel/tracing/set_ftrace_pid: cannot skip to specified offset
id
0+1 records in
0+1 records out
3 bytes copied, 0.000202112 s, 14.8 kB/s
Notice that it only prints "id" and not the "no pid" afterward.
Link: http://lkml.kernel.org/r/4f87c6ad-f114-30bb-8506-c32274ce2992@virtuozzo.com
https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/ftrace.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 71a40e5c3a9f..2ae98f8bce81 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5455,9 +5455,10 @@ static void *fpid_next(struct seq_file *m, void *v, loff_t *pos) struct trace_array *tr = m->private; struct trace_pid_list *pid_list = rcu_dereference_sched(tr->function_pids); - if (v == FTRACE_NO_PIDS) + if (v == FTRACE_NO_PIDS) { + (*pos)++; return NULL; - + } return trace_pid_next(pid_list, v, pos); } |