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x86: fix execve with -fstack-protect

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pointed out by pageexec@freemail.hu:

> what happens here is that gcc treats the argument area as owned by the
> callee, not the caller and is allowed to do certain tricks. for ssp it
> will make a copy of the struct passed by value into the local variable
> area and pass *its* address down, and it won't copy it back into the
> original instance stored in the argument area.
>
> so once sys_execve returns, the pt_regs passed by value hasn't at all
> changed and its default content will cause a nice double fault (FWIW,
> this part took me the longest to debug, being down with cold didn't
> help it either ;).

To fix this we pass in pt_regs by pointer.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Ingo Molnar 2008-02-26 12:55:57 +01:00
parent ce28b9864b
commit 5d119b2c9a
2 changed files with 7 additions and 5 deletions
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6
arch/x86/kernel/entry_64.S
View file

@ -453,6 +453,7 @@ ENTRY(stub_execve)
CFI_REGISTER rip, r11
SAVE_REST
FIXUP_TOP_OF_STACK %r11
movq %rsp, %rcx
call sys_execve
RESTORE_TOP_OF_STACK %r11
movq %rax,RAX(%rsp)
@ -1036,15 +1037,16 @@ ENDPROC(child_rip)
* rdi: name, rsi: argv, rdx: envp
*
* We want to fallback into:
* extern long sys_execve(char *name, char **argv,char **envp, struct pt_regs regs)
* extern long sys_execve(char *name, char **argv,char **envp, struct pt_regs *regs)
*
* do_sys_execve asm fallback arguments:
* rdi: name, rsi: argv, rdx: envp, fake frame on the stack
* rdi: name, rsi: argv, rdx: envp, rcx: fake frame on the stack
*/
ENTRY(kernel_execve)
CFI_STARTPROC
FAKE_STACK_FRAME $0
SAVE_ALL
movq %rsp,%rcx
call sys_execve
movq %rax, RAX(%rsp)
RESTORE_REST

6
arch/x86/kernel/process_64.c
View file

@ -730,16 +730,16 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
*/
asmlinkage
long sys_execve(char __user *name, char __user * __user *argv,
char __user * __user *envp, struct pt_regs regs)
char __user * __user *envp, struct pt_regs *regs)
{
long error;
char * filename;
filename = getname(name);
error = PTR_ERR(filename);
if (IS_ERR(filename))
if (IS_ERR(filename))
return error;
error = do_execve(filename, argv, envp, &regs);
error = do_execve(filename, argv, envp, regs);
putname(filename);
return error;
}