CVE-2023-52574

In the Linux kernel, the following vulnerability has been resolved:

team: fix null-ptr-deref when team device type is changed

Get a null-ptr-deref bug as follows with reproducer [1].

BUG: kernel NULL pointer dereference, address: 0000000000000228 … RIP: 0010:vlan_dev_hard_header+0x35/0x140 [8021q] … Call Trace: ? __die+0x24/0x70 ? page_fault_oops+0x82/0x150 ? exc_page_fault+0x69/0x150 ? asm_exc_page_fault+0x26/0x30 ? vlan_dev_hard_header+0x35/0x140 [8021q] ? vlan_dev_hard_header+0x8e/0x140 [8021q] neigh_connected_output+0xb2/0x100 ip6_finish_output2+0x1cb/0x520 ? nf_hook_slow+0x43/0xc0 ? ip6_mtu+0x46/0x80 ip6_finish_output+0x2a/0xb0 mld_sendpack+0x18f/0x250 mld_ifc_work+0x39/0x160 process_one_work+0x1e6/0x3f0 worker_thread+0x4d/0x2f0 ? __pfx_worker_thread+0x10/0x10 kthread+0xe5/0x120 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x34/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30

[1] $ teamd -t team0 -d -c {runner: {name: loadbalance}} $ ip link add name t-dummy type dummy $ ip link add link t-dummy name t-dummy.100 type vlan id 100 $ ip link add name t-nlmon type nlmon $ ip link set t-nlmon master team0 $ ip link set t-nlmon nomaster $ ip link set t-dummy up $ ip link set team0 up $ ip link set t-dummy.100 down $ ip link set t-dummy.100 master team0

When enslave a vlan device to team device and team device type is changed from non-ether to ether, header_ops of team device is changed to vlan_header_ops. That is incorrect and will trigger null-ptr-deref for vlan->real_dev in vlan_dev_hard_header() because team device is not a vlan device.

Cache eth_header_ops in team_setup(), then assign cached header_ops to header_ops of team net device when its type is changed from non-ether to ether to fix the bug.

Weakness

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/1779eb51b9cc628cee551f252701a85a2a50a457
• https://git.kernel.org/stable/c/2f0acb0736ecc3eb85dc80ad2790d634dcb10b58
• https://git.kernel.org/stable/c/492032760127251e5540a5716a70996bacf2a3fd
• https://git.kernel.org/stable/c/a7fb47b9711101d2405b0eb1276fb1f9b9b270c7
• https://git.kernel.org/stable/c/b44dd92e2afd89eb6e9d27616858e72a67bdc1a7
• https://git.kernel.org/stable/c/c5f6478686bb45f453031594ae19b6c9723a780d
• https://git.kernel.org/stable/c/cac50d9f5d876be32cb9aa21c74018468900284d
• https://git.kernel.org/stable/c/cd05eec2ee0cc396813a32ef675634e403748255
• https://git.kernel.org/stable/c/1779eb51b9cc628cee551f252701a85a2a50a457
• https://git.kernel.org/stable/c/2f0acb0736ecc3eb85dc80ad2790d634dcb10b58
• https://git.kernel.org/stable/c/492032760127251e5540a5716a70996bacf2a3fd
• https://git.kernel.org/stable/c/a7fb47b9711101d2405b0eb1276fb1f9b9b270c7
• https://git.kernel.org/stable/c/b44dd92e2afd89eb6e9d27616858e72a67bdc1a7
• https://git.kernel.org/stable/c/c5f6478686bb45f453031594ae19b6c9723a780d
• https://git.kernel.org/stable/c/cac50d9f5d876be32cb9aa21c74018468900284d
• https://git.kernel.org/stable/c/cd05eec2ee0cc396813a32ef675634e403748255