This is a note to let you know that I've just added the patch titled
x86/sev: Annotate stack change in the #VC handler
to the 5.15-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-sev-annotate-stack-change-in-the-vc-handler.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 250a11a47c7b117fbb5cd4c6a921512df923d75e
Author: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
Date: Wed Mar 16 12:16:12 2022 +0800
x86/sev: Annotate stack change in the #VC handler
[ Upstream commit c42b145181aafd59ed31ccd879493389e3ea5a08 ]
In idtentry_vc(), vc_switch_off_ist() determines a safe stack to
switch to, off of the IST stack. Annotate the new stack switch with
ENCODE_FRAME_POINTER in case UNWINDER_FRAME_POINTER is used.
A stack walk before looks like this:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0-rc7+ #2
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Call Trace:
<TASK>
dump_stack_lvl
dump_stack
kernel_exc_vmm_communication
asm_exc_vmm_communication
? native_read_msr
? __x2apic_disable.part.0
? x2apic_setup
? cpu_init
? trap_init
? start_kernel
? x86_64_start_reservations
? x86_64_start_kernel
? secondary_startup_64_no_verify
</TASK>
and with the fix, the stack dump is exact:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0-rc7+ #3
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Call Trace:
<TASK>
dump_stack_lvl
dump_stack
kernel_exc_vmm_communication
asm_exc_vmm_communication
RIP: 0010:native_read_msr
Code: ...
< snipped regs >
? __x2apic_disable.part.0
x2apic_setup
cpu_init
trap_init
start_kernel
x86_64_start_reservations
x86_64_start_kernel
secondary_startup_64_no_verify
</TASK>
[ bp: Test in a SEV-ES guest and rewrite the commit message to
explain what exactly this does. ]
Fixes: a13644f3a53d ("x86/entry/64: Add entry code for #VC handler")
Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220316041612.71357-1-jiangshanlai@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index e23319ad3f42..3acf0af49305 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -499,6 +499,7 @@ SYM_CODE_START(\asmsym)
call vc_switch_off_ist
movq %rax, %rsp /* Switch to new stack */
+ ENCODE_FRAME_POINTER
UNWIND_HINT_REGS
/* Update pt_regs */
