Commit e04eb52b authored by Guilherme G. Piccoli's avatar Guilherme G. Piccoli Committed by Jonathan Corbet
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Documentation: Document the kernel flag bdev_allow_write_mounted 



Commit ed5cc702 ("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: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarGuilherme G. Piccoli <gpiccoli@igalia.com>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240828145045.309835-1-gpiccoli@igalia.com
parent 34ea875c

Documentation/admin-guide/kernel-parameters.txt

+12 −0
Original line number Diff line number Diff line
@@ -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 mounted block device

			for 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.