Patchwork [v1,2/4] clone3: switch to copy_struct_from_user()

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Submitter Aleksa Sarai
Date Sept. 25, 2019, 4:59 p.m.
Message ID <20190925165915.8135-3-cyphar@cyphar.com>
Download mbox | patch
Permalink /patch/34658/
State New
Headers show

Comments

Aleksa Sarai - Sept. 25, 2019, 4:59 p.m.
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 <cyphar@cyphar.com>
---
 include/uapi/linux/sched.h |  2 ++
 kernel/fork.c              | 34 +++++++---------------------------
 2 files changed, 9 insertions(+), 27 deletions(-)
Christian Brauner - Sept. 25, 2019, 5:22 p.m.
On Wed, Sep 25, 2019 at 06:59:13PM +0200, Aleksa Sarai wrote:
> 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 <cyphar@cyphar.com>
> ---
>  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 541fd805fb88..a86e3841ee4e 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -2530,39 +2530,19 @@ 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;
> -
> -	if (unlikely(size < sizeof(struct clone_args)))
> +	if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
>  		return -EINVAL;

You might want to rebase this patchset after the merge window closes on
rc1 since that code has changed right before the 5.3 release. But if you
can't don't worry I can also fix it up.

Christian

Patch

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 541fd805fb88..a86e3841ee4e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2530,39 +2530,19 @@  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;
-
-	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