This is a note to let you know that I've just added the patch titled
Revert "x86: Fix get_wchan() to support the ORC unwinder"
to the 5.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-x86-fix-get_wchan-to-support-the-orc-unwinder.patch
and it can be found in the queue-5.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f0cdb38335be7346e391e079d2036807e9b1e02c Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 18 Nov 2021 13:16:12 +0100
Subject: Revert "x86: Fix get_wchan() to support the ORC unwinder"
From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
This reverts commit f270511247a5b6257b84db17883e0b1189bf5e16 which is
commit bc9bbb81730ea667c31c5b284f95ee312bab466f upstream.
It has been reported to be causing problems, and is being reworked
upstream and has been dropped from the current 5.15.y stable queue until
it gets resolved.
Reported-by: Chris Rankin <rankincj@xxxxxxxxx>
Reported-by: Thorsten Leemhuis <linux@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/ed000478-2a60-0066-c337-a04bffc112b1@xxxxxxxxxxxxx
Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Sasha Levin <sashal@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/process.c | 51 +++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 48 insertions(+), 3 deletions(-)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -945,13 +945,58 @@ unsigned long arch_randomize_brk(struct
*/
unsigned long get_wchan(struct task_struct *p)
{
- unsigned long entry = 0;
+ unsigned long start, bottom, top, sp, fp, ip, ret = 0;
+ int count = 0;
if (p == current || task_is_running(p))
return 0;
- stack_trace_save_tsk(p, &entry, 1, 0);
- return entry;
+ if (!try_get_task_stack(p))
+ return 0;
+
+ start = (unsigned long)task_stack_page(p);
+ if (!start)
+ goto out;
+
+ /*
+ * Layout of the stack page:
+ *
+ * ----------- topmax = start + THREAD_SIZE - sizeof(unsigned long)
+ * PADDING
+ * ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING
+ * stack
+ * ----------- bottom = start
+ *
+ * The tasks stack pointer points at the location where the
+ * framepointer is stored. The data on the stack is:
+ * ... IP FP ... IP FP
+ *
+ * We need to read FP and IP, so we need to adjust the upper
+ * bound by another unsigned long.
+ */
+ top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
+ top -= 2 * sizeof(unsigned long);
+ bottom = start;
+
+ sp = READ_ONCE(p->thread.sp);
+ if (sp < bottom || sp > top)
+ goto out;
+
+ fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
+ do {
+ if (fp < bottom || fp > top)
+ goto out;
+ ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
+ if (!in_sched_functions(ip)) {
+ ret = ip;
+ goto out;
+ }
+ fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
+ } while (count++ < 16 && !task_is_running(p));
+
+out:
+ put_task_stack(p);
+ return ret;
}
long do_arch_prctl_common(struct task_struct *task, int option,
Patches currently in stable-queue which might be from gregkh@xxxxxxxxxxxxxxxxxxx are
queue-5.14/revert-x86-fix-__get_wchan-for-stacktrace.patch
queue-5.14/revert-x86-fix-get_wchan-to-support-the-orc-unwinder.patch
queue-5.14/revert-sched-add-wrapper-for-get_wchan-to-keep-task-blocked.patch
