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tracing: Hold trace_types_lock when resetting last boot data from readers

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update_last_data_if_empty() is called from tracing_open() with O_TRUNC,
tracing_read_pipe() and tracing_buffers_read() without trace_types_lock.
Two readers can both pass the LAST_BOOT test and free module_delta
twice, and a module notifier can update module_delta while it is being
freed.

Take trace_types_lock in those paths and keep the callers that already
hold it on an unlocked variant.

Cc: stable@vger.kernel.org
Fixes: 32dc004252 ("tracing: Reset last-boot buffers when reading out all cpu buffers")
Link: https://patch.msgid.link/20261016061638.214847-2-devnexen@gmail.com
Signed-off-by: David Carlier <devnexen@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
David Carlier 2026-10-16 07:16:35 +01:00 committed by Steven Rostedt
parent 66877a312a
commit 5a6bd62f09
1 changed files with 16 additions and 3 deletions
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19
kernel/trace/trace.c
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@ -3603,6 +3603,7 @@ static int tracing_single_release_tr(struct inode *inode, struct file *file)
return single_release(inode, file);
}
static bool __update_last_data_if_empty(struct trace_array *tr);
static bool update_last_data_if_empty(struct trace_array *tr);
static int tracing_open(struct inode *inode, struct file *file)
@ -4697,7 +4698,7 @@ tracing_set_trace_read(struct file *filp, char __user *ubuf,
int tracer_init(struct tracer *t, struct trace_array *tr)
{
tracing_reset_online_cpus(&tr->array_buffer);
update_last_data_if_empty(tr);
__update_last_data_if_empty(tr);
return t->init(tr);
}
@ -5371,8 +5372,10 @@ static int tracing_wait_pipe(struct file *filp)
return 1;
}
static bool update_last_data_if_empty(struct trace_array *tr)
static bool __update_last_data_if_empty(struct trace_array *tr)
{
lockdep_assert_held(&trace_types_lock);
if (!(tr->flags & TRACE_ARRAY_FL_LAST_BOOT))
return false;
@ -5387,6 +5390,16 @@ static bool update_last_data_if_empty(struct trace_array *tr)
return true;
}
static bool update_last_data_if_empty(struct trace_array *tr)
{
/* Avoid the lock on the read path unless this is a last boot buffer */
if (!(tr->flags & TRACE_ARRAY_FL_LAST_BOOT))
return false;
guard(mutex)(&trace_types_lock);
return __update_last_data_if_empty(tr);
}
/*
* Consumer reader.
*/
@ -6476,7 +6489,7 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr)
ring_buffer_set_clock(tr->snapshot_buffer.buffer, trace_clocks[i].func);
tracing_reset_online_cpus(&tr->snapshot_buffer);
#endif
update_last_data_if_empty(tr);
__update_last_data_if_empty(tr);
if (tr->scratch && !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) {
struct trace_scratch *tscratch = tr->scratch;