6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Zilin Guan <zilin@xxxxxxxxxx>
commit d65474033740ded0a4fe9a097fce72328655b41d upstream.
In __ftrace_return_to_handler(), a loop iterates over the fgraph_array[]
elements, which are fgraph_ops. The loop checks if an element is a
fgraph_stub to prevent using a fgraph_stub afterward.
However, if the compiler reloads fgraph_array[] after this check, it might
race with an update to fgraph_array[] that introduces a fgraph_stub. This
could result in the stub being processed, but the stub contains a null
"func_hash" field, leading to a NULL pointer dereference.
To ensure that the gops compared against the fgraph_stub matches the gops
processed later, add a READ_ONCE(). A similar patch appears in commit
63a8dfb ("function_graph: Add READ_ONCE() when accessing fgraph_array[]").
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 37238abe3cb47 ("ftrace/function_graph: Pass fgraph_ops to function graph callbacks")
Link: https://lore.kernel.org/20241231113731.277668-1-zilin@xxxxxxxxxx
Signed-off-by: Zilin Guan <zilin@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/fgraph.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -802,7 +802,7 @@ static unsigned long __ftrace_return_to_
#endif
{
for_each_set_bit(i, &bitmap, sizeof(bitmap) * BITS_PER_BYTE) {
- struct fgraph_ops *gops = fgraph_array[i];
+ struct fgraph_ops *gops = READ_ONCE(fgraph_array[i]);
if (gops == &fgraph_stub)
continue;
