[PATCH v5 12/17] perf: Skip user unwind if !current->mm

[Steven Rostedt]

From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

If the task doesn't have any memory, there's no stack to unwind.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
Note from v4: https://lore.kernel.org/all/24cde1381495cd637f0d5663ab7629572bc0eca6.1737511963.git.jpoimboe@xxxxxxxxxx/

- From the previous version, Peter Zijlstra brought up concern about
  io_uring helpers, but this was never resolved. No update was made.

 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 009f34bd9e63..40b98b05fb7c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8101,7 +8101,7 @@ struct perf_callchain_entry *
 perf_callchain(struct perf_event *event, struct pt_regs *regs)
 {
 	bool kernel = !event->attr.exclude_callchain_kernel;
-	bool user   = !event->attr.exclude_callchain_user;
+	bool user   = !event->attr.exclude_callchain_user && current->mm;
 	/* Disallow cross-task user callchains. */
 	bool crosstask = event->ctx->task && event->ctx->task != current;
 	const u32 max_stack = event->attr.sample_max_stack;
-- 
2.47.2