The change is very straightforward, and takes advantage of the (very minor) efficiency improvements in copy_struct_from_user() -- that the memchr_inv() check is done on a buffer instead of one-at-at-time with get_user().
Additionally, explicitly define CLONE_ARGS_SIZE_VER0 to match the other users of the struct-extension pattern.
Cc: Christian Brauner christian@brauner.io Signed-off-by: Aleksa Sarai cyphar@cyphar.com --- include/uapi/linux/sched.h | 2 ++ kernel/fork.c | 34 ++++++---------------------------- 2 files changed, 8 insertions(+), 28 deletions(-)
diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index b3105ac1381a..0945805982b4 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -47,6 +47,8 @@ struct clone_args { __aligned_u64 tls; };
+#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */ + /* * Scheduling policies */ diff --git a/kernel/fork.c b/kernel/fork.c index 2852d0e76ea3..70c10d9b429a 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2528,39 +2528,17 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, #ifdef __ARCH_WANT_SYS_CLONE3 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, struct clone_args __user *uargs, - size_t size) + size_t usize) { + int err; struct clone_args args;
- if (unlikely(size > PAGE_SIZE)) - return -E2BIG; - - if (unlikely(size < sizeof(struct clone_args))) + if (unlikely(usize < CLONE_ARGS_SIZE_VER0)) return -EINVAL;
- if (unlikely(!access_ok(uargs, size))) - return -EFAULT; - - if (size > sizeof(struct clone_args)) { - unsigned char __user *addr; - unsigned char __user *end; - unsigned char val; - - addr = (void __user *)uargs + sizeof(struct clone_args); - end = (void __user *)uargs + size; - - for (; addr < end; addr++) { - if (get_user(val, addr)) - return -EFAULT; - if (val) - return -E2BIG; - } - - size = sizeof(struct clone_args); - } - - if (copy_from_user(&args, uargs, size)) - return -EFAULT; + err = copy_struct_from_user(&args, sizeof(args), uargs, usize); + if (err) + return err;
*kargs = (struct kernel_clone_args){ .flags = args.flags,