+++ Nicholas Piggin [15/06/21 12:05 +1000]:
Excerpts from Jessica Yu's message of June 14, 2021 10:06 pm:
+++ Nicholas Piggin [11/06/21 19:39 +1000]:
The elf_check_arch() function is used to test usermode binaries, but
kernel modules may have more specific requirements. powerpc would like
to test for ABI version compatibility.
Add an arch-overridable function elf_check_module_arch() that defaults
to elf_check_arch() and use it in elf_validity_check().
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
[np: split patch, added changelog]
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
include/linux/moduleloader.h | 5 +++++
kernel/module.c | 2 +-
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
index 9e09d11ffe5b..fdc042a84562 100644
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -13,6 +13,11 @@
* must be implemented by each architecture.
*/
+// Allow arch to optionally do additional checking of module ELF header
+#ifndef elf_check_module_arch
+#define elf_check_module_arch elf_check_arch
+#endif
Hi Nicholas,
Why not make elf_check_module_arch() consistent with the other
arch-specific functions? Please see module_frob_arch_sections(),
module_{init,exit}_section(), etc in moduleloader.h. That is, they are
all __weak functions that are overridable by arches. We can maybe make
elf_check_module_arch() a weak symbol, available for arches to
override if they want to perform additional elf checks. Then we don't
have to have this one-off #define.
Like this? I like it. Good idea.
Yeah! Also, maybe we can alternatively make elf_check_module_arch() a
separate check entirely so that the powerpc implementation doesn't
have to include that extra elf_check_arch() call. Something like this maybe?
diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
index 9e09d11ffe5b..2f9ebd593b4f 100644
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -39,6 +39,9 @@ bool module_init_section(const char *name);
*/
bool module_exit_section(const char *name);
+/* Arch may override to do additional checking of ELF header architecture */
+int elf_check_module_arch(Elf_Ehdr *hdr);
+
/*
* Apply the given relocation to the (simplified) ELF. Return -error
* or 0.
diff --git a/kernel/module.c b/kernel/module.c
index fdd6047728df..9963a979ed54 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2923,6 +2923,11 @@ static int validate_section_offset(struct load_info
*info, Elf_Shdr *shdr)
return 0;
}
+int __weak elf_check_module_arch(Elf_Ehdr *hdr)
+{
+ return 1;
+}
+
/*
* Sanity checks against invalid binaries, wrong arch, weird elf version.
*
@@ -2941,6 +2946,7 @@ static int elf_validity_check(struct load_info *info)
if (memcmp(info->hdr->e_ident, ELFMAG, SELFMAG) != 0
|| info->hdr->e_type != ET_REL
|| !elf_check_arch(info->hdr)
+ || !elf_check_module_arch(info->hdr)
|| info->hdr->e_shentsize != sizeof(Elf_Shdr))
return -ENOEXEC;
