Re: [PATCH v4] nvme: bound FDP config log reads to the received buffer

[Keith Busch <kbusch@kernel.org>]

On Tue, Oct 13, 2026 at 07:28:12PM +0900, Yehyeong Lee wrote:
> nvme_query_fdp_granularity() parses the FDP Configurations log using
> sizes the controller returns, without checking that they fit the buffer
> it was given.  The log size is only bounded from above before
> kvmalloc(), so a size below the log header makes
> le16_to_cpu(h->numfdpc) read past the allocation, and a size of zero
> yields ZERO_SIZE_PTR and faults.  Each configuration descriptor is then
> dereferenced (dsze while walking, and nrg and runs on the selected one)
> without checking that the whole descriptor lies within the buffer, so a
> descriptor at or past the end is read out of bounds.  The out-of-bounds
> runs value is then exposed to userspace through
> /sys/block/nvmeXnY/queue/write_stream_granularity.
> 
> A device-supplied dsze that is not a multiple of eight also leaves the
> following descriptors unaligned, and the structure is not packed, so
> reading nrg and runs from one can fault on architectures without
> efficient unaligned access.

Thanks, applied to nvme-7.4.