2020-05-25 16:14:18

by Horatiu Vultur

Subject: [PATCH] bridge: mrp: Fix out-of-bounds read in br_mrp_parse

The issue was reported by syzbot. When the function br_mrp_parse was
called with a valid net_bridge_port, the net_bridge was an invalid
pointer. Therefore the check br->stp_enabled could pass/fail
depending where it was pointing in memory.
The fix consists of setting the net_bridge pointer if the port is a
valid pointer.

Reported-by: [email protected]
Fixes: 6536993371fa ("bridge: mrp: Integrate MRP into the bridge")
Signed-off-by: Horatiu Vultur <[email protected]>
---
net/bridge/br_mrp_netlink.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/net/bridge/br_mrp_netlink.c b/net/bridge/br_mrp_netlink.c
index 397e7f710772a..4a08a99519b04 100644
--- a/net/bridge/br_mrp_netlink.c
+++ b/net/bridge/br_mrp_netlink.c
@@ -27,6 +27,12 @@ int br_mrp_parse(struct net_bridge *br, struct net_bridge_port *p,
struct nlattr *tb[IFLA_BRIDGE_MRP_MAX + 1];
int err;

+ /* When this function is called for a port then the br pointer is
+ * invalid, therefor set the br to point correctly
+ */
+ if (p)
+ br = p->br;
+
if (br->stp_enabled != BR_NO_STP) {
NL_SET_ERR_MSG_MOD(extack, "MRP can't be enabled if STP is already enabled");
return -EINVAL;
--
2.26.2

2020-05-25 16:25:54

by Nikolay Aleksandrov

Subject: Re: [PATCH] bridge: mrp: Fix out-of-bounds read in br_mrp_parse

On 25/05/2020 12:55, Horatiu Vultur wrote:
> The issue was reported by syzbot. When the function br_mrp_parse was
> called with a valid net_bridge_port, the net_bridge was an invalid
> pointer. Therefore the check br->stp_enabled could pass/fail
> depending where it was pointing in memory.
> The fix consists of setting the net_bridge pointer if the port is a
> valid pointer.
>
> Reported-by: [email protected]
> Fixes: 6536993371fa ("bridge: mrp: Integrate MRP into the bridge")
> Signed-off-by: Horatiu Vultur <[email protected]>
> ---
> net/bridge/br_mrp_netlink.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/net/bridge/br_mrp_netlink.c b/net/bridge/br_mrp_netlink.c
> index 397e7f710772a..4a08a99519b04 100644
> --- a/net/bridge/br_mrp_netlink.c
> +++ b/net/bridge/br_mrp_netlink.c
> @@ -27,6 +27,12 @@ int br_mrp_parse(struct net_bridge *br, struct net_bridge_port *p,
> struct nlattr *tb[IFLA_BRIDGE_MRP_MAX + 1];
> int err;
>
> + /* When this function is called for a port then the br pointer is
> + * invalid, therefor set the br to point correctly
> + */
> + if (p)
> + br = p->br;
> +
> if (br->stp_enabled != BR_NO_STP) {
> NL_SET_ERR_MSG_MOD(extack, "MRP can't be enabled if STP is already enabled");
> return -EINVAL;
>

You should tag the fix for net-next when it's intended for it.

Acked-by: Nikolay Aleksandrov <[email protected]>

2020-05-26 01:13:00

by David Miller

Subject: Re: [PATCH] bridge: mrp: Fix out-of-bounds read in br_mrp_parse

From: Horatiu Vultur <[email protected]>
Date: Mon, 25 May 2020 09:55:41 +0000

> The issue was reported by syzbot. When the function br_mrp_parse was
> called with a valid net_bridge_port, the net_bridge was an invalid
> pointer. Therefore the check br->stp_enabled could pass/fail
> depending where it was pointing in memory.
> The fix consists of setting the net_bridge pointer if the port is a
> valid pointer.
>
> Reported-by: [email protected]
> Fixes: 6536993371fa ("bridge: mrp: Integrate MRP into the bridge")
> Signed-off-by: Horatiu Vultur <[email protected]>

Applied to net-next, thanks.