Re: [PATCH] nvme: core: reject invalid LBA data size from Identify Namespace

["Maurizio Lombardi" <mlombard@arkamax.eu>]

On Sat Apr 18, 2026 at 6:28 AM CEST, Chao Shi wrote:
> nvme_update_ns_info_block() trusts id->lbaf[lbaf].ds from the
> controller and assigns it directly to ns->head->lba_shift without
> bounds checking.  nvme_lba_to_sect() then does:
>
>     return lba << (head->lba_shift - SECTOR_SHIFT);
>
> When called with lba = le64_to_cpu(id->nsze) to compute the device
> capacity, an attacker-controlled controller can choose ds < 9 or a
> combination of (ds, nsze) that makes the left shift overflow
> sector_t.  The former is a C undefined behaviour that UBSAN reports
> as a BUG; the latter silently yields a bogus capacity that the
> block layer then trusts for bounds checking.
>
> Validate ds against SECTOR_SHIFT and use check_shl_overflow() to
> compute capacity so that any (ds, nsze) combination that would
> overflow sector_t is rejected.  The namespace is skipped with -EIO
> instead of crashing the kernel.  This is reachable by a malicious
> NVMe device, a buggy firmware, or an attacker-controlled NVMe-oF
> target.
>
> Stack trace (UBSAN, ds < 9 variant):
>
>   RIP: nvme_lba_to_sect drivers/nvme/host/nvme.h:699 [inline]
>   RIP: nvme_update_ns_info_block.cold+0x5/0x7
>   Call Trace:
>    nvme_update_ns_info+0x175/0xd90 drivers/nvme/host/core.c:2467
>    nvme_validate_ns drivers/nvme/host/core.c:4299 [inline]
>    nvme_scan_ns drivers/nvme/host/core.c:4350
>    nvme_scan_ns_async+0xa5/0xe0 drivers/nvme/host/core.c:4383
>    async_run_entry_fn
>    process_one_work
>    worker_thread
>    kthread
>
> Found by Syzkaller.
>
> Fixes: 9419e71b8d67 ("nvme: move ns id info to struct nvme_ns_head")
> Acked-by: Sungwoo Kim <iam@sung-woo.kim>
> Acked-by: Dave Tian <daveti@purdue.edu>
> Acked-by: Weidong Zhu <weizhu@fiu.edu>
> Signed-off-by: Chao Shi <coshi036@gmail.com>
> ---
>  drivers/nvme/host/core.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 1e33af94c24..9b3bf3e4075 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2407,9 +2407,19 @@ static int nvme_update_ns_info_block(struct nvme_ns *ns,
>  	lim = queue_limits_start_update(ns->disk->queue);
>  
>  	memflags = blk_mq_freeze_queue(ns->disk->queue);
> +	if (id->lbaf[lbaf].ds < SECTOR_SHIFT ||
> +	    check_shl_overflow(le64_to_cpu(id->nsze),
> +			       id->lbaf[lbaf].ds - SECTOR_SHIFT,
> +			       &capacity)) {
> +		dev_warn_once(ns->ctrl->device,
> +			"invalid LBA data size %u, skipping namespace\n",
> +			id->lbaf[lbaf].ds);

Just a nit:

If I'm reading the NVMe spec correctly, ds == 0 has a special meaning:
'LBA format is not currently available.'
maybe we should use a different dev_warn() for ds == 0 ?

Maurizio