This is a note to let you know that I've just added the patch titled
x86/entry/64: Fix unwind hints in kernel exit path
to the 5.6-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:
x86-entry-64-fix-unwind-hints-in-kernel-exit-path.patch
and it can be found in the queue-5.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1fb143634a38095b641a3a21220774799772dc4c Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Sat, 25 Apr 2020 05:03:02 -0500
Subject: x86/entry/64: Fix unwind hints in kernel exit path
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
commit 1fb143634a38095b641a3a21220774799772dc4c upstream.
In swapgs_restore_regs_and_return_to_usermode, after the stack is
switched to the trampoline stack, the existing UNWIND_HINT_REGS hint is
no longer valid, which can result in the following ORC unwinder warning:
WARNING: can't dereference registers at 000000003aeb0cdd for ip swapgs_restore_regs_and_return_to_usermode+0x93/0xa0
For full correctness, we could try to add complicated unwind hints so
the unwinder could continue to find the registers, but when when it's
this close to kernel exit, unwind hints aren't really needed anymore and
it's fine to just use an empty hint which tells the unwinder to stop.
For consistency, also move the UNWIND_HINT_EMPTY in
entry_SYSCALL_64_after_hwframe to a similar location.
Fixes: 3e3b9293d392 ("x86/entry/64: Return to userspace from the trampoline stack")
Reported-by: Vince Weaver <vincent.weaver@xxxxxxxxx>
Reported-by: Dave Jones <dsj@xxxxxx>
Reported-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx>
Reported-by: Joe Mario <jmario@xxxxxxxxxx>
Reported-by: Jann Horn <jannh@xxxxxxxxxx>
Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/60ea8f562987ed2d9ace2977502fe481c0d7c9a0.1587808742.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/entry/entry_64.S | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -249,7 +249,6 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_h
*/
syscall_return_via_sysret:
/* rcx and r11 are already restored (see code above) */
- UNWIND_HINT_EMPTY
POP_REGS pop_rdi=0 skip_r11rcx=1
/*
@@ -258,6 +257,7 @@ syscall_return_via_sysret:
*/
movq %rsp, %rdi
movq PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
+ UNWIND_HINT_EMPTY
pushq RSP-RDI(%rdi) /* RSP */
pushq (%rdi) /* RDI */
@@ -637,6 +637,7 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_
*/
movq %rsp, %rdi
movq PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
+ UNWIND_HINT_EMPTY
/* Copy the IRET frame to the trampoline stack. */
pushq 6*8(%rdi) /* SS */
Patches currently in stable-queue which might be from jpoimboe@xxxxxxxxxx are
queue-5.6/x86-entry-64-fix-unwind-hints-in-kernel-exit-path.patch
queue-5.6/x86-unwind-orc-don-t-skip-the-first-frame-for-inactive-tasks.patch
queue-5.6/x86-unwind-orc-prevent-unwinding-before-orc-initialization.patch
queue-5.6/x86-entry-64-fix-unwind-hints-in-__switch_to_asm.patch
queue-5.6/x86-unwind-orc-fix-error-path-for-bad-orc-entry-type.patch
queue-5.6/x86-entry-64-fix-unwind-hints-in-rewind_stack_do_exit.patch
queue-5.6/x86-unwind-orc-fix-premature-unwind-stoppage-due-to-iret-frames.patch
queue-5.6/x86-entry-64-fix-unwind-hints-in-register-clearing-code.patch
queue-5.6/objtool-fix-stack-offset-tracking-for-indirect-cfas.patch
queue-5.6/kvm-vmx-explicitly-clear-rflags.cf-and-rflags.zf-in-vm-exit-rsb-path.patch
