On Wed, Aug 28, 2024 at 09:27:53AM GMT, Darrick J. Wong wrote:

On Wed, Aug 28, 2024 at 11:48:58AM -0300, Guilherme G. Piccoli wrote:

quoted

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@acm.org>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>

Looks good to me now,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

Fun unrelated question: do we want to turn on bdev_allow_write_mounted
if lockdown is enabled?  In that kind of environment, we don't want to
allow random people to scribble, given how many weird ext4 bugs we've
had to fix due to syzbot.

I would say yes, we absolutely do.