Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=75154f402ef18e459ff97ddece25656b6c2b329c
Commit:     75154f402ef18e459ff97ddece25656b6c2b329c
Parent:     e2f1f19272f8de0374ad297b9806f8b6509e0013
Author:     Andi Kleen <[EMAIL PROTECTED]>
AuthorDate: Sat Jun 23 02:29:25 2007 +0200
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Fri Jun 22 18:41:19 2007 -0700

    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: [EMAIL PROTECTED]
    Signed-off-by: Andi Kleen <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 arch/x86_64/kernel/entry.S   |    7 +++++++
 arch/x86_64/kernel/setup64.c |    3 +++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index fa984b5..a67f87b 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -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)
diff --git a/arch/x86_64/kernel/setup64.c b/arch/x86_64/kernel/setup64.c
index 64379a8..1200aaa 100644
--- a/arch/x86_64/kernel/setup64.c
+++ b/arch/x86_64/kernel/setup64.c
@@ -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 ();
-
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