Linux Kernel CVE-2025-40350

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

net/mlx5e: RX, Fix generating skb from non-linear xdp_buff for striding RQ

XDP programs can change the layout of an xdp_buff through bpf_xdp_adjust_tail() and bpf_xdp_adjust_head(). Therefore, the driver cannot assume the size of the linear data area nor fragments. Fix the bug in mlx5 by generating skb according to xdp_buff after XDP programs run.

Currently, when handling multi-buf XDP, the mlx5 driver assumes the layout of an xdp_buff to be unchanged. That is, the linear data area continues to be empty and fragments remain the same. This may cause the driver to generate erroneous skb or triggering a kernel warning. When an XDP program added linear data through bpf_xdp_adjust_head(), the linear data will be ignored as mlx5e_build_linear_skb() builds an skb without linear data and then pull data from fragments to fill the linear data area. When an XDP program has shrunk the non-linear data through bpf_xdp_adjust_tail(), the delta passed to __pskb_pull_tail() may exceed the actual nonlinear data size and trigger the BUG_ON in it.

To fix the issue, first record the original number of fragments. If the number of fragments changes after the XDP program runs, rewind the end fragment pointer by the difference and recalculate the truesize. Then, build the skb with the linear data area matching the xdp_buff. Finally, only pull data in if there is non-linear data and fill the linear part up to 256 bytes.

The affected product is the Linux kernel, specifically the net/mlx5e driver used by NVIDIA/Mellanox ConnectX-family network adapters, on systems using striding receive queues with multi-buffer XDP. Exact affected version ranges are not provided in the input (no CPE strings were supplied and CWE is N/A); the four stable-tree commits at git.kernel.org (87bcef1, 8b051d7, cb9edd5, f2557d7) indicate the fix was backported across multiple stable branches, implying several longterm kernel series were affected. Administrators should map these commit hashes to their distribution's kernel package to determine exposure. No dedicated vendor advisory URL beyond the kernel.org commit references was included.