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Subject[PATCH v1 2/4] clone3: switch to copy_struct_from_user()
Date
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;

- 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
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