From 5d119b2c9a490e2d647eae134211b32a18a04c7d Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 26 Feb 2008 12:55:57 +0100 Subject: [PATCH] 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 Signed-off-by: Thomas Gleixner --- arch/x86/kernel/entry_64.S | 6 ++++-- arch/x86/kernel/process_64.c | 6 +++--- 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 2ad9a1bc6a73..c20c9e7e08dd 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -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 diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index b0cc8f0136d8..43f287744f9f 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -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, ®s); + error = do_execve(filename, argv, envp, regs); putname(filename); return error; } -- 2.30.2