linux-kernel - [PATCH] x86/callthunks: Correct calculation of dest address in is

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Message-Id: <20231201085727.3647051-1-ubizjak@gmail.com>
Date:   Fri,  1 Dec 2023 09:57:27 +0100
From:   Uros Bizjak <ubizjak@...il.com>
To:     x86@...nel.org, llvm@...ts.linux.dev, linux-kernel@...r.kernel.org
Cc:     Uros Bizjak <ubizjak@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH] x86/callthunks: Correct calculation of dest address in is_callthunk()

GCC didn't warn on the invalid use of relocation destination
pointer, so the calculated destination value was applied to
the uninitialized pointer location in error.

Fixes: 17bce3b2ae2d ("x86/callthunks: Handle %rip-relative relocations in call thunk template")
Reported-by: Nathan Chancellor <nathan@...nel.org>
Closes: https://lore.kernel.org/lkml/20231201035457.GA321497@dev-arch.thelio-3990X/
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Uros Bizjak <ubizjak@...il.com>
---
 arch/x86/kernel/callthunks.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index f5507c95e7be..c561dd481eb9 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -306,7 +306,7 @@ static bool is_callthunk(void *addr)
 	if (!thunks_initialized || skip_addr((void *)dest))
 		return false;
 
-	*pad = dest - tmpl_size;
+	pad = (void *)(dest - tmpl_size);
 
 	memcpy(insn_buff, skl_call_thunk_template, tmpl_size);
 	apply_relocation(insn_buff, tmpl_size, pad,
-- 
2.31.1