On 20/08/2024 13:23, Darrick J. Wong wrote:

[...]

quoted

+	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.

Can we mention that this also solves the problem of naïve storage
management tools (aka the ones that don't use O_EXCL) writing over a
mounted filesystem and trashing it?

--D

Sure! At least from my side, fine with that.
How about the following string ?

+ 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. Also prevents issues from direct writes
+ of silly storage tooling (that doesn't use O_EXCL). The
+ default is Y and can be changed through the Kconfig
+ option CONFIG_BLK_DEV_WRITE_MOUNTED.


But feel free to improve / change it. I'll wait more feedback and
resubmit with a refined text.
Cheers,


Guilherme