linux-kernel - Re: [PATCH] [v2] block: fix FS_IOC_GETLBMD_CAP parsing in blkdev_common

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Message-ID: <CADYN=9KHYSQRLk00RZUygSD28CwfmbpjWa+W+P7B5xgB9vPCsQ@mail.gmail.com>
Date: Fri, 11 Jul 2025 11:40:13 +0200
From: Anders Roxell <anders.roxell@...aro.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Anuj Gupta <anuj20.g@...sung.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, 
	Kanchan Joshi <joshi.k@...sung.com>, Christian Brauner <brauner@...nel.org>, 
	Christoph Hellwig <hch@...radead.org>, Arnd Bergmann <arnd@...db.de>, 
	Naresh Kamboju <naresh.kamboju@...aro.org>, Jens Axboe <axboe@...nel.dk>, 
	Keith Busch <kbusch@...nel.org>, Caleb Sander Mateos <csander@...estorage.com>, 
	Pavel Begunkov <asml.silence@...il.com>, Alexey Dobriyan <adobriyan@...il.com>, 
	"Darrick J. Wong" <djwong@...nel.org>, linux-block@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] block: fix FS_IOC_GETLBMD_CAP parsing in blkdev_common_ioctl()

On Fri, 11 Jul 2025 at 10:47, Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> 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@mail.gmail.com/
> Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
> Cc: Anders Roxell <anders.roxell@...aro.org>
> Cc: Naresh Kamboju <naresh.kamboju@...aro.org>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Tested-by: Anders Roxell <anders.roxell@...aro.org>

Tested it in qemu-aarch64, it now ran the ltp-smoke test fine.

Cheers,
Anders

> ---
> 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.
> ---
>  block/blk-integrity.c | 10 ++++++----
>  block/ioctl.c         |  6 ++++--
>  2 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/block/blk-integrity.c b/block/blk-integrity.c
> index 9d9dc9c32083..61a79e19c78f 100644
> --- a/block/blk-integrity.c
> +++ b/block/blk-integrity.c
> @@ -62,10 +62,12 @@ int blk_get_meta_cap(struct block_device *bdev, unsigned int cmd,
>         struct logical_block_metadata_cap meta_cap = {};
>         size_t usize = _IOC_SIZE(cmd);
>
> -       if (!argp)
> -               return -EINVAL;
> -       if (usize < LBMD_SIZE_VER0)
> -               return -EINVAL;
> +       if (_IOC_DIR(cmd)  != _IOC_DIR(FS_IOC_GETLBMD_CAP) ||
> +           _IOC_TYPE(cmd) != _IOC_TYPE(FS_IOC_GETLBMD_CAP) ||
> +           _IOC_NR(cmd)   != _IOC_NR(FS_IOC_GETLBMD_CAP) ||
> +           _IOC_SIZE(cmd) < LBMD_SIZE_VER0)
> +               return -ENOIOCTLCMD;
> +
>         if (!bi)
>                 goto out;
>
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 9ad403733e19..af2e22e5533c 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -566,9 +566,11 @@ static int blkdev_common_ioctl(struct block_device *bdev, blk_mode_t mode,
>                                void __user *argp)
>  {
>         unsigned int max_sectors;
> +       int ret;
>
> -       if (_IOC_NR(cmd) == _IOC_NR(FS_IOC_GETLBMD_CAP))
> -               return blk_get_meta_cap(bdev, cmd, argp);
> +       ret = blk_get_meta_cap(bdev, cmd, argp);
> +       if (ret != -ENOIOCTLCMD)
> +               return ret;
>
>         switch (cmd) {
>         case BLKFLSBUF:
> --
> 2.39.5
>