[PATCH 5.4 116/155] xfrm: fix uctx len check in verify_sec_ctx_len

Greg Kroah-Hartman
2020-03-31T09:16:52Z

From: Xin Long <lucien.xin@gmail.com>

commit 171d449a028573b2f0acdc7f31ecbb045391b320 upstream.

It's not sufficient to do 'uctx->len != (sizeof(struct xfrm_user_sec_ctx) +
uctx->ctx_len)' check only, as uctx->len may be greater than nla_len(rt),
in which case it will cause slab-out-of-bounds when accessing uctx->ctx_str
later.

This patch is to fix it by return -EINVAL when uctx->len > nla_len(rt).

Fixes: df71837d5024 ("[LSM-IPSec]: Security association restriction.")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/xfrm/xfrm_user.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -110,7 +110,8 @@ static inline int verify_sec_ctx_len(str
return 0;

uctx = nla_data(rt);
- if (uctx->len != (sizeof(struct xfrm_user_sec_ctx) + uctx->ctx_len))
+ if (uctx->len > nla_len(rt) ||
+ uctx->len != (sizeof(struct xfrm_user_sec_ctx) + uctx->ctx_len))
return -EINVAL;

return 0;