On 8/23/24 12:05 PM, 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>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
> ---
>
> V3: Dropped reference to page cache (thanks Bart!).
>
> V2 link: https://lore.kernel.org/r/20240823142840.63234-1-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..58b9455baf4a 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 of directly writing to mounted block
Since we're nit picking...
Control the ability to directly write [...]
The directly may be a bit confusing ("does it mean O_DIRECT?"), so maybe
just
Control the ability to write [...]
would be better and more clear.
> + devices, i.e., allow / disallow writes that bypasses the
Since we're nit picking, s/bypasses/bypass
> + 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.
--
Jens Axboe
