Re: [PATCH] nvmet: passthru: fix OOB reads when parsing ns id descriptor list

[Christoph Hellwig <hch@lst.de>]

On Fri, Jul 17, 2026 at 04:43:53PM +0200, Hari Mishal wrote:
> nvmet_passthru_override_id_descs() walks a namespace identification
> descriptor list populated from the underlying passthru controller's
> Identify response, which is device reported. The loop advanced pos by
> device controlled amounts (sizeof(*cur) + nidl) without checking that
> the next descriptor header actually fits inside the buffer, so a
> malicious device could push pos to within a few bytes of the buffer end
> and cause cur->nidl, cur->nidt or the reserved field to be read past the
> allocation.
> 
> Additionally, when a CSI descriptor lands exactly at the last valid
> header offset, cur + 1 points one byte past the end of the buffer.
> The unconditional memcpy(&csi, cur + 1, NVME_NIDT_CSI_LEN) could read
> that out-of-bounds byte and copy it back to the initiator via
> nvmet_copy_to_sgl(), leaking adjacent heap memory.
> 
> Bounds check both the descriptor header and the CSI value before
> dereferencing them.
> 
> Signed-off-by: Hari Mishal <harimishal1@gmail.com>
> ---
>  drivers/nvme/target/passthru.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
> index e27f84e3cf2b..7ef02958078b 100644
> --- a/drivers/nvme/target/passthru.c
> +++ b/drivers/nvme/target/passthru.c
> @@ -53,13 +53,21 @@ static u16 nvmet_passthru_override_id_descs(struct nvmet_req *req)
>  	for (pos = 0; pos < NVME_IDENTIFY_DATA_SIZE; pos += len) {
>  		struct nvme_ns_id_desc *cur = data + pos;
>  
> +		if (pos + sizeof(*cur) > NVME_IDENTIFY_DATA_SIZE)
> +			break;
> +
>  		if (cur->nidl == 0)
>  			break;
> +
>  		if (cur->nidt == NVME_NIDT_CSI) {
> +			if (pos + sizeof(*cur) + NVME_NIDT_CSI_LEN > NVME_IDENTIFY_DATA_SIZE)

Overly long line here.  Otherwise this looks sane.