6.4-stable review patch. If anyone has any objections, please let me know.
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From: Brian Foster bfoster@redhat.com
commit 3d07fa1dd19035eb0b13ae6697efd5caa9033e74 upstream.
The pipe cpumask used to serialize opens between the main and percpu trace pipes is not zeroed or initialized. This can result in spurious -EBUSY returns if underlying memory is not fully zeroed. This has been observed by immediate failure to read the main trace_pipe file on an otherwise newly booted and idle system:
# cat /sys/kernel/debug/tracing/trace_pipe cat: /sys/kernel/debug/tracing/trace_pipe: Device or resource busy
Zero the allocation of pipe_cpumask to avoid the problem.
Link: https://lore.kernel.org/linux-trace-kernel/20230831125500.986862-1-bfoster@r...
Cc: stable@vger.kernel.org Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes") Reviewed-by: Zheng Yejian zhengyejian1@huawei.com Reviewed-by: Masami Hiramatsu (Google) mhiramat@kernel.org Signed-off-by: Brian Foster bfoster@redhat.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/trace.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9465,7 +9465,7 @@ static struct trace_array *trace_array_c if (!alloc_cpumask_var(&tr->tracing_cpumask, GFP_KERNEL)) goto out_free_tr;
- if (!alloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL)) + if (!zalloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL)) goto out_free_tr;
tr->trace_flags = global_trace.trace_flags & ~ZEROED_TRACE_FLAGS; @@ -10410,7 +10410,7 @@ __init static int tracer_alloc_buffers(v if (trace_create_savedcmd() < 0) goto out_free_temp_buffer;
- if (!alloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL)) + if (!zalloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL)) goto out_free_savedcmd;
/* TODO: make the number of buffers hot pluggable with CPUS */