[PATCH] Documentation: Document the kernel flag bdev_allow_write_mounted

["Guilherme G. Piccoli" <gpiccoli@igalia.com>]

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.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 09126bb8cc9f..709d1ee342db 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -517,6 +517,16 @@
 			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
+			devices' page cache, i.e., allow / disallow writes that
+			bypasses the FS. This was implemented as a means to
+			prevent fuzzers to crash the kernel by breaking the
+			filesystem without its awareness, through direct block
+			device writes. 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.
 
-- 
2.45.2