6.1-stable review patch. If anyone has any objections, please let me know.
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From: Johannes Wikner kwikner@ethz.ch
commit 50e4b3b94090babe8d4bb85c95f0d3e6b07ea86e upstream.
entry_ibpb() should invalidate all indirect predictions, including return target predictions. Not all IBPB implementations do this, in which case the fallback is RSB filling.
Prevent SRSO-style hijacks of return predictions following IBPB, as the return target predictor can be corrupted before the IBPB completes.
[ bp: Massage. ]
Signed-off-by: Johannes Wikner kwikner@ethz.ch Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/entry/entry.S | 5 +++++ 1 file changed, 5 insertions(+)
--- a/arch/x86/entry/entry.S +++ b/arch/x86/entry/entry.S @@ -9,6 +9,8 @@ #include <asm/unwind_hints.h> #include <asm/segment.h> #include <asm/cache.h> +#include <asm/cpufeatures.h> +#include <asm/nospec-branch.h>
.pushsection .noinstr.text, "ax"
@@ -17,6 +19,9 @@ SYM_FUNC_START(entry_ibpb) movl $PRED_CMD_IBPB, %eax xorl %edx, %edx wrmsr + + /* Make sure IBPB clears return stack preductions too. */ + FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_BUG_IBPB_NO_RET RET SYM_FUNC_END(entry_ibpb) /* For KVM */