Merge branch 'net-start-to-replace-copy_from_sockptr'

Eric Dumazet says:

====================
net: start to replace copy_from_sockptr()

We got several syzbot reports about unsafe copy_from_sockptr()
calls. After fixing some of them, it appears that we could
use a new helper to factorize all the checks in one place.

This series targets net tree, we can later start converting
many call sites in net-next.
====================

Link: https://lore.kernel.org/r/20240408082845.3957374-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
index 307961b41541..317200cd3a60 100644
--- a/include/linux/sockptr.h
+++ b/include/linux/sockptr.h
@@ -50,11 +50,36 @@ static inline int copy_from_sockptr_offset(void *dst, sockptr_t src,
 	return 0;
 }
 
+/* Deprecated.
+ * This is unsafe, unless caller checked user provided optlen.
+ * Prefer copy_safe_from_sockptr() instead.
+ */
 static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
 {
 	return copy_from_sockptr_offset(dst, src, 0, size);
 }
 
+/**
+ * copy_safe_from_sockptr: copy a struct from sockptr
+ * @dst:   Destination address, in kernel space. This buffer must be @ksize
+ *         bytes long.
+ * @ksize: Size of @dst struct.
+ * @optval: Source address. (in user or kernel space)
+ * @optlen: Size of @optval data.
+ *
+ * Returns:
+ *  * -EINVAL: @optlen < @ksize
+ *  * -EFAULT: access to userspace failed.
+ *  * 0 : @ksize bytes were copied
+ */
+static inline int copy_safe_from_sockptr(void *dst, size_t ksize,
+					 sockptr_t optval, unsigned int optlen)
+{
+	if (optlen < ksize)
+		return -EINVAL;
+	return copy_from_sockptr(dst, optval, ksize);
+}
+
 static inline int copy_struct_from_sockptr(void *dst, size_t ksize,
 		sockptr_t src, size_t usize)
 {