Re: [PATCH v3] nvme: bound FDP config log reads to the received buffer

[Kanchan Joshi <joshi.k@samsung.com>]

On 10/8/2026 11:54 PM, Yehyeong Lee wrote:
> v3: read the descriptor fields with get_unaligned_le*() since a device-supplied
> dsze can leave subsequent descriptors unaligned, which could fault on
> architectures without efficient unaligned access.

Were you able to test this part.

> v2: allocate the log buffer with kvzalloc() so that if the controller completes
> the Get Log Page with a short transfer, the uninitialized tail reads as zero
> and is rejected by the existing dsze check instead of being parsed (hardening).
> v1:https://lore.kernel.org/linux-nvme/20261008132604.1168105-1- 
> yhlee@isslab.korea.ac.kr/
> 
>   drivers/nvme/host/core.c | 24 ++++++++++++++++++++----
>   1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 9bcab3dc4c118..094df0e6ed326 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2272,13 +2272,17 @@ static int nvme_query_fdp_granularity(struct nvme_ctrl *ctrl,
>   	}
>   
>   	size = le32_to_cpu(hdr.sze);
> +	if (size < sizeof(*h)) {

header plus at least one descriptor is expected. So this can changed to:

if (size < sizeof(hdr) + sizeof(*desc)) {

  > +		dev_warn(ctrl->device, "FDP config log too small\n");
> +		return 0;
> +	}
>   	if (size > PAGE_SIZE * MAX_ORDER_NR_PAGES) {
>   		dev_warn(ctrl->device, "FDP config size too large:%zu\n",
>   			 size);
>   		return 0;
>   	}
>   
> -	h = kvmalloc(size, GFP_KERNEL);
> +	h = kvzalloc(size, GFP_KERNEL);
>   	if (!h)
>   		return -ENOMEM;
>   
> @@ -2304,8 +2308,12 @@ static int nvme_query_fdp_granularity(struct nvme_ctrl *ctrl,
>   	desc = log;
>   	end = log + size - sizeof(*h);
>   	for (i = 0; i < fdp_idx; i++) {
> -		u16 dsze = le16_to_cpu(desc->dsze);
> +		u16 dsze;
>   
> +		if ((u8 *)desc + sizeof(*desc) > (u8 *)h + size)
> +			goto short_desc;

This and other short_desc check can be covered by extending the existing 
check below

> +
> +		dsze = get_unaligned_le16(&desc->dsze);
>   		if (!dsze || log + dsze > end) {

here, by checking that next descriptor fits completely.
Also !dsze does not cover other invalid values from 1 to 63.

Overall, something like this:

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 7eb0f9fe6b18..9991cff5c332 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2273,13 +2273,19 @@ static int nvme_query_fdp_granularity(struct 
nvme_ctrl *ctrl,
         }

         size = le32_to_cpu(hdr.sze);
+       if (size < sizeof(hdr) + sizeof(*desc)) {
+               dev_warn(ctrl->device, "FDP config size too small:%zu\n",
+                               size);
+               return 0;
+       }
+
         if (size > PAGE_SIZE * MAX_ORDER_NR_PAGES) {
                 dev_warn(ctrl->device, "FDP config size too large:%zu\n",
                          size);
                 return 0;
         }

-       h = kvmalloc(size, GFP_KERNEL);
+       h = kvzalloc(size, GFP_KERNEL);
         if (!h)
                 return -ENOMEM;

@@ -2305,9 +2311,10 @@ static int nvme_query_fdp_granularity(struct 
nvme_ctrl *ctrl,
         desc = log;
         end = log + size - sizeof(*h);
         for (i = 0; i < fdp_idx; i++) {
-               u16 dsze = le16_to_cpu(desc->dsze);
+               u16 dsze = get_unaligned_le16(&desc->dsze);

-               if (!dsze || log + dsze > end) {
+               /* next descriptor must fit within the log */
+               if (dsze < sizeof(*desc) || log + dsze + sizeof(*desc) > 
end) {
                         dev_warn(ctrl->device,
                                  "FDP invalid config descriptor at 
index %d\n", i);
                         ret = 0;
@@ -2317,13 +2324,13 @@ static int nvme_query_fdp_granularity(struct 
nvme_ctrl *ctrl,
                 desc = log;
         }

-       if (le32_to_cpu(desc->nrg) > 1) {
+       if (get_unaligned_le32(&desc->nrg) > 1) {
                 dev_warn(ctrl->device, "FDP NRG > 1 not supported\n");
                 ret = 0;
                 goto out;
         }

-       info->runs = le64_to_cpu(desc->runs);
+       info->runs = get_unaligned_le64(&desc->runs);
  out:
         kvfree(h);
         return ret;