CVE-2024-46857 net/mlx5: Fix bridge mode operations when there are no VFs
A local attacker can cause a kernel crash by setting bridge mode on a network interface with no virtual functions, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-46857?
CVE-2024-46857 is a medium-severity vulnerability in Linux kernel, published on 27 Sep 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5: Fix bridge mode operations when there are no VFs
Currently, trying to set the bridge mode attribute when numvfs=0 leads to a crash:
bridge link set dev eth2 hwmode vepa
[ 168.967392] BUG: kernel NULL pointer dereference, address: 0000000000000030 [...] [ 168.969989] RIP: 0010:mlx5_add_flow_rules+0x1f/0x300 [mlx5_core] [...] [ 168.976037] Call Trace: [ 168.976188] <TASK> [ 168.978620] _mlx5_eswitch_set_vepa_locked+0x113/0x230 [mlx5_core] [ 168.979074] mlx5_eswitch_set_vepa+0x7f/0xa0 [mlx5_core] [ 168.979471] rtnl_bridge_setlink+0xe9/0x1f0 [ 168.979714] rtnetlink_rcv_msg+0x159/0x400 [ 168.980451] netlink_rcv_skb+0x54/0x100 [ 168.980675] netlink_unicast+0x241/0x360 [ 168.980918] netlink_sendmsg+0x1f6/0x430 [ 168.981162] ____sys_sendmsg+0x3bb/0x3f0 [ 168.982155] ___sys_sendmsg+0x88/0xd0 [ 168.985036] __sys_sendmsg+0x59/0xa0 [ 168.985477] do_syscall_64+0x79/0x150 [ 168.987273] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 168.987773] RIP: 0033:0x7f8f7950f917
(esw->fdb_table.legacy.vepa_fdb is null)
The bridge mode is only relevant when there are multiple functions per port. Therefore, prevent setting and getting this setting when there are no VFs.
Note that after this change, there are no settings to change on the PF interface using `bridge link` when there are no VFs, so the interface no longer appears in the `bridge link` output.
Weakness: CWE-476
Which versions are affected by CVE-2024-46857?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-46857?
Apply the vendor's patch.
Is CVE-2024-46857 being exploited?
There is no known exploitation of CVE-2024-46857 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-49784, AZL-49788, BELL-CVE-2024-46857, DEBIAN-CVE-2024-46857, GHSA-3rw3-pfv7-m7r7, ROOT-OS-DEBIAN-11-CVE-2024-46857 and 2 more.