Re: [PATCH] arm64/module: set trampoline section flags regardless of CONFIG_DYNAMIC_FTRACE
From: Ard Biesheuvel <ardb@kernel.org>
Date: 2020-09-02 06:01:28
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On Tue, 1 Sep 2020 at 19:00, Jessica Yu [off-list ref] wrote:
In the arm64 module linker script, the section .text.ftrace_trampoline
is specified unconditionally regardless of whether CONFIG_DYNAMIC_FTRACE
is enabled (this is simply due to the limitation that module linker
scripts are not preprocessed like the vmlinux one).
Normally, for .plt and .text.ftrace_trampoline, the section flags
present in the module binary wouldn't matter since module_frob_arch_sections()
would assign them manually anyway. However, the arm64 module loader only
sets the section flags for .text.ftrace_trampoline when CONFIG_DYNAMIC_FTRACE=y.
That's only become problematic recently due to a recent change in
binutils-2.35, where the .text.ftrace_trampoline section (along with the
.plt section) is now marked writable and executable (WAX).
We no longer allow writable and executable sections to be loaded due to
commit 5c3a7db0c7ec ("module: Harden STRICT_MODULE_RWX"), so this is
causing all modules linked with binutils-2.35 to be rejected under arm64.
Drop the IS_ENABLED(CONFIG_DYNAMIC_FTRACE) check in module_frob_arch_sections()
so that the section flags for .text.ftrace_trampoline get properly set to
SHF_EXECINSTR|SHF_ALLOC, without SHF_WRITE.
Link: http://lore.kernel.org/r/20200831094651.GA16385@linux-8ccs (local)
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Jessica Yu <jeyu@kernel.org>Acked-by: Ard Biesheuvel <ardb@kernel.org>
quoted hunk ↗ jump to hunk
--- arch/arm64/kernel/module-plts.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)diff --git a/arch/arm64/kernel/module-plts.c b/arch/arm64/kernel/module-plts.c index 0ce3a28e3347..2e224435c024 100644 --- a/arch/arm64/kernel/module-plts.c +++ b/arch/arm64/kernel/module-plts.c@@ -305,8 +305,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, mod->arch.core.plt_shndx = i; else if (!strcmp(secstrings + sechdrs[i].sh_name, ".init.plt")) mod->arch.init.plt_shndx = i; - else if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE) && - !strcmp(secstrings + sechdrs[i].sh_name, + else if (!strcmp(secstrings + sechdrs[i].sh_name, ".text.ftrace_trampoline")) tramp = sechdrs + i; else if (sechdrs[i].sh_type == SHT_SYMTAB) --2.16.4
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