[PATCH 6.8 157/336] net: add copy_safe_from_sockptr() helper

Greg Kroah-Hartman
2024-05-14T10:37:24Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 6309863b31dd80317cd7d6824820b44e254e2a9c ]

copy_from_sockptr() helper is unsafe, unless callers
did the prior check against user provided optlen.

Too many callers get this wrong, lets add a helper to
fix them and avoid future copy/paste bugs.

Instead of :

if (optlen < sizeof(opt)) {
err = -EINVAL;
break;
}
if (copy_from_sockptr(&opt, optval, sizeof(opt)) {
err = -EFAULT;
break;
}

Use :

err = copy_safe_from_sockptr(&opt, sizeof(opt),
optval, optlen);
if (err)
break;

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240408082845.3957374-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/sockptr.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
index 307961b41541a..317200cd3a603 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)
{
--
2.43.0