CVE-2026-80789

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

nvmet-tcp: bound SGL data length before allocating command buffers

nvmet_tcp_map_data() reads the host-controlled 32-bit sgl->length and, for the in-capsule offset descriptor (type 0x01), checks it against port->inline_data_size before use. Any other SGL descriptor type – including the non-inline transport SGL data-block descriptor (type (NVME_TRANSPORT_SGL_DATA_DESC « 4) | NVME_SGL_FMT_TRANSPORT_A, the type a real host uses for out-of-capsule writes) skips that check entirely and falls straight through to:

cmd->req.sg = sgl_alloc(len, GFP_KERNEL, &cmd->req.sg_cnt);

with len taken directly from the wire, unbounded up to 4 GiB.

nvmet_req_init() only parses the command and never inspects sgl->length, and nvmet_check_transfer_len() – the only other place transfer_len is validated – runs later, from req->execute(), after the allocation has already happened. For a write command the target responds with an R2T and parks the command waiting for the host to send the data; if the host (or an unauthenticated peer that simply never follows up) never does, the sgl_alloc() buffer stays resident for the life of the command. NVMe/TCP has no mandatory authentication in the default configuration, so any peer able to reach the target portal and complete a Fabrics connect can drive this with a single crafted command, repeatable across queues and connections for amplification. This is unbounded kernel memory allocation triggered by a remote, effectively unauthenticated peer.

Validate len against the same NVMET_TCP_MAXH2CDATA ceiling this file already uses to bound per-PDU H2C data, for every SGL descriptor type, before doing any allocation. This closes the gap for the non-inline descriptor while leaving the existing, tighter inline_data_size check in place for the in-capsule case.

Runtime-verified on a v6.19 KASAN stand: with this bound in place, a crafted write command carrying an oversized non-inline SGL length is rejected before sgl_alloc() runs, where the same request previously drove an unbounded ~256 MiB kernel allocation (up to 4 GiB) that stayed resident pending an R2T the host never satisfies.

Affected Software

References

• https://git.kernel.org/stable/c/0952541b153e258b99d39cdb03ea6919fdeb41d0
• https://git.kernel.org/stable/c/14dbe37681a6a7e346fc147bb363ec7cca3180a0
• https://git.kernel.org/stable/c/25ad03d5c0e858c4b63f1e4b6d461d2af1b30b22
• https://git.kernel.org/stable/c/4a3f00262a044e8e15064b1a6860968bf0500bf4
• https://git.kernel.org/stable/c/6d27199ebe8cb223022150f74be13f154a964474
• https://git.kernel.org/stable/c/d2acc96c528d589f5827cfb90e8e9229dd9d8cb4
• https://git.kernel.org/stable/c/d895e66628f939edbb98608f6e033d3d39e6e546
• https://git.kernel.org/stable/c/f63e89a0310264264923f84406dea05fe752de62
• https://git.kernel.org/stable/c/f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5