diff options
| author | Steven Rostedt <rostedt@goodmis.org> | 2024-08-08 23:57:30 -0400 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2024-08-09 12:59:35 -0400 |
| commit | d0949cd44a62c4c41b30ea7ae94d8c887f586882 (patch) | |
| tree | 58604728c96f7b6a02b994fbaa90b6a779473e1a /kernel | |
| parent | 0b6743bd60a56a701070b89fb80c327a44b7b3e2 (diff) | |
tracing: Return from tracing_buffers_read() if the file has been closed
When running the following:
# cd /sys/kernel/tracing/
# echo 1 > events/sched/sched_waking/enable
# echo 1 > events/sched/sched_switch/enable
# echo 0 > tracing_on
# dd if=per_cpu/cpu0/trace_pipe_raw of=/tmp/raw0.dat
The dd task would get stuck in an infinite loop in the kernel. What would
happen is the following:
When ring_buffer_read_page() returns -1 (no data) then a check is made to
see if the buffer is empty (as happens when the page is not full), it will
call wait_on_pipe() to wait until the ring buffer has data. When it is it
will try again to read data (unless O_NONBLOCK is set).
The issue happens when there's a reader and the file descriptor is closed.
The wait_on_pipe() will return when that is the case. But this loop will
continue to try again and wait_on_pipe() will again return immediately and
the loop will continue and never stop.
Simply check if the file was closed before looping and exit out if it is.
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20240808235730.78bf63e5@rorschach.local.home
Fixes: 2aa043a55b9a7 ("tracing/ring-buffer: Fix wait_on_pipe() race")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/trace.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 10cd38bce2f1..ebe7ce2f5f4a 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7956,7 +7956,7 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, trace_access_unlock(iter->cpu_file); if (ret < 0) { - if (trace_empty(iter)) { + if (trace_empty(iter) && !iter->closed) { if ((filp->f_flags & O_NONBLOCK)) return -EAGAIN; |