This is a note to let you know that I've just added the patch titled
x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro
to the 6.5-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-tdx-zero-out-the-missing-rsi-in-tdx_hypercall-ma.patch
and it can be found in the queue-6.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ccd79c457465306dd38a0ad48b8fa1f2fefe0074
Author: Kai Huang <kai.huang@xxxxxxxxx>
Date: Tue Aug 15 23:01:55 2023 +1200
x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro
[ Upstream commit 5d092b66119d774853cc9308522620299048a662 ]
In the TDX_HYPERCALL asm, after the TDCALL instruction returns from the
untrusted VMM, the registers that the TDX guest shares to the VMM need
to be cleared to avoid speculative execution of VMM-provided values.
RSI is specified in the bitmap of those registers, but it is missing
when zeroing out those registers in the current TDX_HYPERCALL.
It was there when it was originally added in commit 752d13305c78
("x86/tdx: Expand __tdx_hypercall() to handle more arguments"), but was
later removed in commit 1e70c680375a ("x86/tdx: Do not corrupt
frame-pointer in __tdx_hypercall()"), which was correct because %rsi is
later restored in the "pop %rsi". However a later commit 7a3a401874be
("x86/tdx: Drop flags from __tdx_hypercall()") removed that "pop %rsi"
but forgot to add the "xor %rsi, %rsi" back.
Fix by adding it back.
Fixes: 7a3a401874be ("x86/tdx: Drop flags from __tdx_hypercall()")
Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/e7d1157074a0b45d34564d5f17f3e0ffee8115e9.1692096753.git.kai.huang%40intel.com
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index b193c0a1d8db3..2eca5f43734fe 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -195,6 +195,7 @@ SYM_FUNC_END(__tdx_module_call)
xor %r10d, %r10d
xor %r11d, %r11d
xor %rdi, %rdi
+ xor %rsi, %rsi
xor %rdx, %rdx
/* Restore callee-saved GPRs as mandated by the x86_64 ABI */
