From 282124d18626379a20b41d25e0c580f290cd09d4 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 30 Sep 2012 13:20:09 -0400 Subject: [PATCH] generic kernel_execve() based mostly on arm and alpha versions. Architectures can define __ARCH_WANT_KERNEL_EXECVE and use it, provided that * they have working current_pt_regs(), even for kernel threads. * kernel_thread-spawned threads do have space for pt_regs in the normal location. Normally that's as simple as switching to generic kernel_thread() and making sure that kernel threads do *not* go through return from syscall path; call the payload from equivalent of ret_from_fork if we are in a kernel thread (or just have separate ret_from_kernel_thread and make copy_thread() use it instead of ret_from_fork in kernel thread case). * they have ret_from_kernel_execve(); it is called after successful do_execve() done by kernel_execve() and gets normal pt_regs location passed to it as argument. It's essentially a longjmp() analog - it should set sp, etc. to the situation expected at the return for syscall and go there. Eventually the need for that sucker will disappear, but that'll take some surgery on kernel_thread() payloads. Signed-off-by: Al Viro --- fs/exec.c | 22 ++++++++++++++++++++++ include/linux/binfmts.h | 5 +++++ 2 files changed, 27 insertions(+) diff --git a/fs/exec.c b/fs/exec.c index d7f9e14f8977..48c525115fe4 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -2318,3 +2318,25 @@ int dump_seek(struct file *file, loff_t off) return ret; } EXPORT_SYMBOL(dump_seek); + +#ifdef __ARCH_WANT_KERNEL_EXECVE +int kernel_execve(const char *filename, + const char *const argv[], + const char *const envp[]) +{ + struct pt_regs *p = current_pt_regs(); + int ret; + + ret = do_execve(filename, + (const char __user *const __user *)argv, + (const char __user *const __user *)envp, p); + if (ret < 0) + return ret; + + /* + * We were successful. We won't be returning to our caller, but + * instead to user space by manipulating the kernel stack. + */ + ret_from_kernel_execve(p); +} +#endif diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 8938beabad7a..f9c9d08f4f7c 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -19,6 +19,7 @@ struct pt_regs; #ifdef __KERNEL__ #include +#include #include #define CORENAME_MAX_SIZE 128 @@ -137,5 +138,9 @@ extern void do_coredump(long signr, int exit_code, struct pt_regs *regs); extern void set_binfmt(struct linux_binfmt *new); extern void free_bprm(struct linux_binprm *); +#ifdef __ARCH_WANT_KERNEL_EXECVE +extern void ret_from_kernel_execve(struct pt_regs *normal) __noreturn; +#endif + #endif /* __KERNEL__ */ #endif /* _LINUX_BINFMTS_H */ -- 2.30.2