On Sat, Jun 03 2023 at 10:52P -0400,
Demi Marie Obenour <d...@invisiblethingslab.com> wrote:
> Especially on 32-bit systems, it is possible for the pointer arithmetic
> to overflow and cause a userspace pointer to be dereferenced in the
> kernel.
>
> Signed-off-by: Demi Marie Obenour <d...@invisiblethingslab.com>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: sta...@vger.kernel.org
> ---
> drivers/md/dm-ioctl.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index
> 34fa74c6a70db8aa67aaba3f6a2fc4f38ef736bc..64e8f16d344c47057de5e2d29e3d63202197dca0
> 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -1396,6 +1396,25 @@ static int next_target(struct dm_target_spec *last,
> uint32_t next, void *end,
> {
> static_assert(_Alignof(struct dm_target_spec) <= 8,
> "struct dm_target_spec has excessive alignment
> requirements");
> + static_assert(offsetof(struct dm_ioctl, data) >= sizeof(struct
> dm_target_spec),
> + "struct dm_target_spec too big");
I'm struggling to see the point for this compile-time check?
Especially when you consider (on x86_64):
sizeof(struct dm_target_spec) = 40
offsetof(struct dm_ioctl, data) = 305
Just feels like there is no utility offered by adding this check.
SO I've dropped it. But if you feel there is some inherent value
please let me know.
Thanks,
Mike
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