CVE-2025-38440 net/mlx5e: Fix race between DIM disable and net_dim()
A race condition in the Linux kernel mlx5 driver causes a NULL pointer dereference, leading to a system crash.
- 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-2025-38440?
CVE-2025-38440 is a high-severity vulnerability in Linux kernel, published on 25 Jul 2025. 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/mlx5e: Fix race between DIM disable and net_dim()
There's a race between disabling DIM and NAPI callbacks using the dim pointer on the RQ or SQ.
If NAPI checks the DIM state bit and sees it still set, it assumes `rq->dim` or `sq->dim` is valid. But if DIM gets disabled right after that check, the pointer might already be set to NULL, leading to a NULL pointer dereference in net_dim().
Fix this by calling `synchronize_net()` before freeing the DIM context. This ensures all in-progress NAPI callbacks are finished before the pointer is cleared.
Kernel log:
BUG: kernel NULL pointer dereference, address: 0000000000000000 ... RIP: 0010:net_dim+0x23/0x190 ... Call Trace: <TASK> ? __die+0x20/0x60 ? page_fault_oops+0x150/0x3e0 ? common_interrupt+0xf/0xa0 ? sysvec_call_function_single+0xb/0x90 ? exc_page_fault+0x74/0x130 ? asm_exc_page_fault+0x22/0x30 ? net_dim+0x23/0x190 ? mlx5e_poll_ico_cq+0x41/0x6f0 [mlx5_core] ? sysvec_apic_timer_interrupt+0xb/0x90 mlx5e_handle_rx_dim+0x92/0xd0 [mlx5_core] mlx5e_napi_poll+0x2cd/0xac0 [mlx5_core] ? mlx5e_poll_ico_cq+0xe5/0x6f0 [mlx5_core] busy_poll_stop+0xa2/0x200 ? mlx5e_napi_poll+0x1d9/0xac0 [mlx5_core] ? mlx5e_trigger_irq+0x130/0x130 [mlx5_core] __napi_busy_loop+0x345/0x3b0 ? sysvec_call_function_single+0xb/0x90 ? asm_sysvec_call_function_single+0x16/0x20 ? sysvec_apic_timer_interrupt+0xb/0x90 ? pcpu_free_area+0x1e4/0x2e0 napi_busy_loop+0x11/0x20 xsk_recvmsg+0x10c/0x130 sock_recvmsg+0x44/0x70 __sys_recvfrom+0xbc/0x130 ? __schedule+0x398/0x890 __x64_sys_recvfrom+0x20/0x30 do_syscall_64+0x4c/0x100 entry_SYSCALL_64_after_hwframe+0x4b/0x53 ... ---[ end trace 0000000000000000 ]--- ... ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
Weakness: CWE-362
Which versions are affected by CVE-2025-38440?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-38440?
Apply the vendor's patch.
Is CVE-2025-38440 being exploited?
There is no known exploitation of CVE-2025-38440 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-38440, DEBIAN-CVE-2025-38440, GHSA-4c77-8jrg-w382, ROOT-OS-UBUNTU-2204-CVE-2025-38440, ROOT-OS-UBUNTU-2404-CVE-2025-38440, UBUNTU-CVE-2025-38440.