x86: fix execve with -fstack-protect
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>
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 2ad9a1b..c20c9e7 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -453,6 +453,7 @@
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 @@
* 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
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index b0cc8f0..43f2877 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -730,16 +730,16 @@
*/
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, ®s);
+ error = do_execve(filename, argv, envp, regs);
putname(filename);
return error;
}