Re: [PATCH] [v2] block: fix FS_IOC_GETLBMD_CAP parsing in blkdev_common_ioctl()

[Christian Brauner]

On Fri, Jul 11, 2025 at 10:46:51AM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> Anders and Naresh found that the addition of the FS_IOC_GETLBMD_CAP
> handling in the blockdev ioctl handler breaks all ioctls with
> _IOC_NR==2, as the new command is not added to the switch but only
> a few of the command bits are check.
> 
> Move the check into the blk_get_meta_cap() function itself and make
> it return -ENOIOCTLCMD for any unsupported command code, including
> those with a smaller size that previously returned -EINVAL.
> 
> For consistency this also drops the check for NULL 'arg' that
> is really useless, as any invalid pointer should return -EFAULT.
> 
> Fixes: 9eb22f7fedfc ("fs: add ioctl to query metadata and protection info capabilities")
> Link: https://lore.kernel.org/all/CA+G9fYvk9HHE5UJ7cdJHTcY6P5JKnp+_e+sdC5U-ZQFTP9_hqQ@xxxxxxxxxxxxxx/
> Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Cc: Anders Roxell <anders.roxell@xxxxxxxxxx>
> Cc: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> v2: add the check in blk-integrity.c instead of ioctl.c
> 
> I've left out the maximum-size check this time, as there was no
> consensus on whether there should be one, or what value.
> 
> We still need to come up with a better way of handling these in
> general, for now the patch just addresses the immediate regression
> that Naresh found.
> 
> I have also sent a handful of patches for other drivers that have
> variations of the same bug.

Arnd, let me know how I can help!