From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 14 Jun 2022 23:15:40 +0200
Subject: x86/ftrace: Use alternative RET encoding
Git-commit: 1f001e9da6bbf482311e45e48f53c2bd2179e59c
Patch-mainline: v5.19-rc7
References: bsc#1203969, bsc#1199657 CVE-2022-29900 CVE-2022-29901
Use the return thunk in ftrace trampolines, if needed.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/ftrace.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 5b4efc927d80..24b9fa89aa27 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -301,7 +301,7 @@ union ftrace_op_code_union {
} __attribute__((packed));
};
-#define RET_SIZE 1 + IS_ENABLED(CONFIG_SLS)
+#define RET_SIZE (IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS))
static unsigned long
create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
@@ -357,7 +357,10 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
goto fail;
ip = trampoline + size;
- memcpy(ip, retq, RET_SIZE);
+ if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
+ __text_gen_insn(ip, JMP32_INSN_OPCODE, ip, &__x86_return_thunk, JMP32_INSN_SIZE);
+ else
+ memcpy(ip, retq, sizeof(retq));
/* No need to test direct calls on created trampolines */
if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {