This is a note to let you know that I've just added the patch titled
x86/retbleed: Fix return thunk alignment
to the 5.10-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-retbleed-fix-return-thunk-alignment.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 9a48d604672220545d209e9996c2a1edbb5637f6 Mon Sep 17 00:00:00 2001
From: "Borislav Petkov (AMD)" <bp@xxxxxxxxx>
Date: Fri, 12 May 2023 23:12:26 +0200
Subject: x86/retbleed: Fix return thunk alignment
From: Borislav Petkov (AMD) <bp@xxxxxxxxx>
commit 9a48d604672220545d209e9996c2a1edbb5637f6 upstream.
SYM_FUNC_START_LOCAL_NOALIGN() adds an endbr leading to this layout
(leaving only the last 2 bytes of the address):
3bff <zen_untrain_ret>:
3bff: f3 0f 1e fa endbr64
3c03: f6 test $0xcc,%bl
3c04 <__x86_return_thunk>:
3c04: c3 ret
3c05: cc int3
3c06: 0f ae e8 lfence
However, "the RET at __x86_return_thunk must be on a 64 byte boundary,
for alignment within the BTB."
Use SYM_START instead.
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/lib/retpoline.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -86,8 +86,8 @@ SYM_CODE_END(__x86_indirect_thunk_array)
*/
.align 64
.skip 63, 0xcc
-SYM_FUNC_START_NOALIGN(zen_untrain_ret);
-
+SYM_START(zen_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+ ANNOTATE_NOENDBR
/*
* As executed from zen_untrain_ret, this is:
*
Patches currently in stable-queue which might be from bp@xxxxxxxxx are
queue-5.10/x86-mce-amd-use-an-u64-for-bank_map.patch
queue-5.10/x86-apic-fix-atomic-update-of-offset-in-reserve_eilv.patch
queue-5.10/x86-retbleed-fix-return-thunk-alignment.patch
