From: Eric Dumazet <edumazet@google.com>

Date: Fri, 17 Feb 2023 18:24:54 +0000

Subject: [PATCH] scm: add user copy checks to put_cmsg()

References: bsc#1012628

Patch-mainline: 6.2.3

Git-commit: 5f1eb1ff58ea122e24adf0bc940f268ed2227462

[ Upstream commit 5f1eb1ff58ea122e24adf0bc940f268ed2227462 ]

This is a followup of commit 2558b8039d05 ("net: use a bounce

buffer for copying skb->mark")

x86 and powerpc define user_access_begin, meaning

that they are not able to perform user copy checks

when using user_write_access_begin() / unsafe_copy_to_user()

and friends [1]

Instead of waiting bugs to trigger on other arches,

add a check_object_size() in put_cmsg() to make sure

that new code tested on x86 with CONFIG_HARDENED_USERCOPY=y

will perform more security checks.

[1] We can not generically call check_object_size() from

unsafe_copy_to_user() because UACCESS is enabled at this point.

Signed-off-by: Eric Dumazet <edumazet@google.com>

Cc: Kees Cook <keescook@chromium.org>

Acked-by: Kees Cook <keescook@chromium.org>

Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Sasha Levin <sashal@kernel.org>

Signed-off-by: Jiri Slaby <jslaby@suse.cz>

---

 net/core/scm.c | 2 ++

 1 file changed, 2 insertions(+)

diff --git a/net/core/scm.c b/net/core/scm.c

index 5c356f0d..acb7d776 100644

--- a/net/core/scm.c

+++ b/net/core/scm.c

@@ -229,6 +229,8 @@ int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)

 	if (msg->msg_control_is_user) {

 		struct cmsghdr __user *cm = msg->msg_control_user;

+		check_object_size(data, cmlen - sizeof(*cm), true);

+

 		if (!user_write_access_begin(cm, cmlen))

 			goto efault;

-- 

2.35.3