linux-kernel - [PATCH v5 12/15] x86, module: Ignore __typeid_

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Message-Id: <20211013181658.1020262-13-samitolvanen@google.com>
Date:   Wed, 13 Oct 2021 11:16:55 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     x86@...nel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH v5 12/15] x86, module: Ignore __typeid__ relocations

The R_X86_64_8 __typeid__* relocations are for constants the compiler
generates for indirect call type checking with CONFIG_CFI_CLANG. Ignore
them when loading modules.

Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Tested-by: Sedat Dilek <sedat.dilek@...il.com>
---
 arch/x86/kernel/module.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 5e9a34b5bd74..c4aeba237eef 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -197,6 +197,10 @@ static int __apply_relocate_add(Elf64_Shdr *sechdrs,
 			val -= (u64)loc;
 			write(loc, &val, 8);
 			break;
+		case R_X86_64_8:
+			if (!strncmp(strtab + sym->st_name, "__typeid__", 10))
+				break;
+			fallthrough;
 		default:
 			pr_err("%s: Unknown rela relocation: %llu\n",
 			       me->name, ELF64_R_TYPE(rel[i].r_info));
-- 
2.33.0.1079.g6e70778dc9-goog