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fgraph: Add READ_ONCE() when accessing fgraph_array[]

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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@vger.kernel.org
Fixes: 37238abe3cb47 ("ftrace/function_graph: Pass fgraph_ops to function graph callbacks")
Link: https://lore.kernel.org/20241231113731.277668-1-zilin@seu.edu.cn
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Zilin Guan 2024-12-31 11:37:31 +00:00 committed by Steven Rostedt (Google)
parent fc033cf25e
commit d654740337
1 changed files with 1 additions and 1 deletions
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2
kernel/trace/fgraph.c
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@ -833,7 +833,7 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
#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;