From 0dc636b3b757a6b747a156de613275f9d74a4a66 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 19 Nov 2021 10:29:47 +0100 Subject: [PATCH] x86: Pin task-stack in __get_wchan() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When commit 5d1ceb3969b6 ("x86: Fix __get_wchan() for !STACKTRACE") moved from stacktrace to native unwind_*() usage, the try_get_task_stack() got lost, leading to use-after-free issues for dying tasks. Signed-off-by: Peter Zijlstra (Intel) Fixes: 5d1ceb3969b6 ("x86: Fix __get_wchan() for !STACKTRACE") Link: https://bugzilla.kernel.org/show_bug.cgi?id=215031 Link: https://lore.kernel.org/stable/YZV02RCRVHIa144u@fedora64.linuxtx.org/ Reported-by: Justin Forbes Reported-by: Holger Hoffstätte Cc: Qi Zheng Cc: Kees Cook Cc: Thomas Gleixner Signed-off-by: Linus Torvalds --- arch/x86/kernel/process.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index e9ee8b526319..04143a653a8a 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -964,6 +964,9 @@ unsigned long __get_wchan(struct task_struct *p) struct unwind_state state; unsigned long addr = 0; + if (!try_get_task_stack(p)) + return 0; + for (unwind_start(&state, p, NULL, NULL); !unwind_done(&state); unwind_next_frame(&state)) { addr = unwind_get_return_address(&state); @@ -974,6 +977,8 @@ unsigned long __get_wchan(struct task_struct *p) break; } + put_task_stack(p); + return addr; }