[v5,30/32] x86/dumpstack: Pin the target stack in save_stack_trace_tsk()

Commit Message

Andy Lutomirski July 11, 2016, 8:54 p.m. UTC

This will prevent a crash if the target task dies before or while
dumping its stack once we start freeing task stacks early.

Signed-off-by: Andy Lutomirski <[e-mail]>
---
 arch/x86/kernel/stacktrace.c | 5 +++++
 1 file changed, 5 insertions(+)

Patch

diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 9ee98eefc44d..cc0826409a21 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -79,9 +79,14 @@  void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 
 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 {
+	if (!try_get_task_stack(tsk))
+		return;
+
 	dump_trace(tsk, NULL, NULL, 0, &save_stack_ops_nosched, trace);
 	if (trace->nr_entries < trace->max_entries)
 		trace->entries[trace->nr_entries++] = ULONG_MAX;
+
+	put_task_stack(tsk);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);