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Commit 75154f40 authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
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x86_64: Ignore compat mode SYSCALL when IA32_EMULATION is not defined 



Previously a program could switch to a compat mode segment and then
execute SYSCALL and it would jump to an uninitialized MSR and crash
the kernel.

Instead supply a dummy target for this case.

Pointed out by Jan Beulich

Cc: jbeulich@novell.com
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e2f1f192

arch/x86_64/kernel/entry.S

+7 −0
Original line number Diff line number Diff line
@@ -1163,3 +1163,10 @@ ENTRY(call_softirq) 
	ret

	CFI_ENDPROC

ENDPROC(call_softirq)



KPROBE_ENTRY(ignore_sysret)

	CFI_STARTPROC

	mov $-ENOSYS,%eax

	sysret

	CFI_ENDPROC

ENDPROC(ignore_sysret)

arch/x86_64/kernel/setup64.c

+3 −0
Original line number Diff line number Diff line
@@ -150,6 +150,8 @@ void pda_init(int cpu) 
char boot_exception_stacks[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]

__attribute__((section(".bss.page_aligned")));



extern asmlinkage void ignore_sysret(void);



/* May not be marked __init: used by software suspend */

void syscall_init(void)

{
@@ -160,6 +162,7 @@ void syscall_init(void) 
	 */ 

	wrmsrl(MSR_STAR,  ((u64)__USER32_CS)<<48  | ((u64)__KERNEL_CS)<<32); 

	wrmsrl(MSR_LSTAR, system_call); 

	wrmsrl(MSR_CSTAR, ignore_sysret);



#ifdef CONFIG_IA32_EMULATION   		

	syscall32_cpu_init ();