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Subject[PATCH RESEND] x86: Reject x32 executables if x32 ABI not supported
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It is currently possible to execve() an x32 executable on an x86_64
kernel that has only ia32 compat enabled. However all its syscalls
will fail, even _exit(). This usually causes it to segfault.

Change the ELF compat architecture check so that x32 executables are
rejected if we don't support the x32 ABI.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/include/asm/elf.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 1a055c8..ca3347a 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -160,8 +160,9 @@ do { \
#define elf_check_arch(x) \
((x)->e_machine == EM_X86_64)

-#define compat_elf_check_arch(x) \
- (elf_check_arch_ia32(x) || (x)->e_machine == EM_X86_64)
+#define compat_elf_check_arch(x) \
+ (elf_check_arch_ia32(x) || \
+ (IS_ENABLED(CONFIG_X86_X32_ABI) && (x)->e_machine == EM_X86_64))

#if __USER32_DS != __USER_DS
# error "The following code assumes __USER32_DS == __USER_DS"

--
Ben Hutchings
Experience is directly proportional to the value of equipment destroyed.
- Carolyn Scheppner
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