linux-kernel - [PATCH AUTOSEL 6.8 24/43] net: add copy_safe_from

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Date: Mon, 22 Apr 2024 19:14:10 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	0x7f454c46@...il.com,
	davem@...emloft.net,
	noureddine@...sta.com,
	dsahern@...nel.org,
	fruggeri@...sta.com
Subject: [PATCH AUTOSEL 6.8 24/43] net: add copy_safe_from_sockptr() helper

From: Eric Dumazet <edumazet@...gle.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@...gle.com>
Link: https://lore.kernel.org/r/20240408082845.3957374-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.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