Re: [PATCH v2] fpga: microchip-spi: add bounds checks in mpf_ops_parse_header()

Greg KH
2026-04-02T16:06:15Z

On Thu, Apr 02, 2026 at 09:37:52AM -0600, Sebastian Alba Vives wrote:
> From: Sebastian Josue Alba Vives <sebasjosue84@gmail.com>
>
> mpf_ops_parse_header() reads several fields from the bitstream file
> and uses them as offsets and sizes without validating them against the
> buffer size, leading to multiple out-of-bounds read vulnerabilities:

Note, bitstream files are "trusted" so this really isn't a
"vulnerability" just a "someone with hardware permissions sent a stupid
file to the kernel" issue :)

> 1. There is no check that count is large enough to read header_size
> at MPF_HEADER_SIZE_OFFSET (24). Add a minimum count check.
>
> 2. When header_size (u8 from file) is 0, the expression
> *(buf + header_size - 1) reads one byte before the buffer.
> Return -EINVAL since retrying with a larger buffer cannot fix
> a zero header_size.
>
> 3. In the block lookup loop, block_id_offset and block_start_offset
> advance by MPF_LOOKUP_TABLE_RECORD_SIZE (9) each iteration with
> blocks_num (u8) controlling the count. With a small buffer, these
> offsets exceed count, causing OOB reads via get_unaligned_le32().
> Return -EAGAIN since a larger buffer may resolve the issue.
>
> 4. components_size_start (from file) and component_size_byte_num
> (derived from components_num, u16 from file) are used as offsets
> into buf without validation, allowing arbitrary OOB reads.
>
> Add bounds checks for all four cases.
>
> Fixes: 5f8d4a9008307 ("fpga: microchip-spi: add Microchip MPF FPGA manager")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sebastian Alba Vives <sebasjosue84@gmail.com>
> ---
> drivers/fpga/microchip-spi.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)

Please look at these review comments:
https://sashiko.dev/#/patchset/20260402153752.3793055-1-sebasjosue84%40gmail.com
this driver is "odd", but some of those comments seem correct.

thansk,

greg k-h