On Sun 25-08-24 21:15:11, Guilherme G. Piccoli wrote:
> Commit ed5cc702d311 ("block: Add config option to not allow writing to mounted
> devices") added a Kconfig option along with a kernel command-line tuning to
> control writes to mounted block devices, as a means to deal with fuzzers like
> Syzkaller, that provokes kernel crashes by directly writing on block devices
> bypassing the filesystem (so the FS has no awareness and cannot cope with that).
>
> The patch just missed adding such kernel command-line option to the kernel
> documentation, so let's fix that.
>
> Cc: Bart Van Assche <bvanassche@xxxxxxx>
> Cc: Darrick J. Wong <djwong@xxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
> ---
>
> V4: More improvements in the wording (thanks Jens and Darrick!)
>
> V3 link: https://lore.kernel.org/r/20240823180635.86163-1-gpiccoli@xxxxxxxxxx
>
>
> Documentation/admin-guide/kernel-parameters.txt | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 09126bb8cc9f..d521d444a35c 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -517,6 +517,18 @@
> Format: <io>,<irq>,<mode>
> See header of drivers/net/hamradio/baycom_ser_hdx.c.
>
> + bdev_allow_write_mounted=
> + Format: <bool>
> + Control the ability to open a block device for
^^ a mounted block device
Otherwise looks good so feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> + writing, i.e., allow / disallow writes that bypass
> + the FS. This was implemented as a means to prevent
> + fuzzers from crashing the kernel by overwriting the
> + metadata underneath a mounted FS without its awareness.
> + This also prevents destructive formatting of mounted
> + filesystems by naive storage tooling that don't use
> + O_EXCL. Default is Y and can be changed through the
> + Kconfig option CONFIG_BLK_DEV_WRITE_MOUNTED.
> +
> bert_disable [ACPI]
> Disable BERT OS support on buggy BIOSes.
>
> --
> 2.46.0
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
