Re: [PATCH RESEND v3 2/4] clone3: switch to copy_struct_from_user()
flat view
From: Kees Cook <hidden>
Date: 2019-09-30 23:42:42
Also in:
lkml
On Tue, Oct 01, 2019 at 05:15:24AM +1000, Aleksa Sarai wrote:
quoted hunk ↗ jump to hunk
From: Aleksa Sarai <redacted> The change is very straightforward, and helps unify the syscall interface for struct-from-userspace syscalls. Additionally, explicitly define CLONE_ARGS_SIZE_VER0 to match the other users of the struct-extension pattern. Signed-off-by: Aleksa Sarai <redacted> --- include/uapi/linux/sched.h | 2 ++ kernel/fork.c | 34 +++++++--------------------------- 2 files changed, 9 insertions(+), 27 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 f9572f416126..2ef529869c64 100644 --- a/kernel/fork.c +++ b/kernel/fork.c@@ -2525,39 +2525,19 @@ 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)) + if (unlikely(usize > PAGE_SIZE)) return -E2BIG;
I quickly looked through the earlier threads and couldn't find it, but
I have a memory of some discussion about moving this test into the
copy_struct_from_user() function itself? That would seems like a
reasonable idea? ("4k should be enough for any structure!")
Either way:
Reviewed-by: Kees Cook <redacted>
-
- 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;
/*
* Verify that higher 32bits of exit_signal are unset and that
--
2.23.0-- Kees Cook