On Fri, Aug 23, 2024 at 12:17:54PM -0600, Jens Axboe wrote: > 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. "Control the ability to open a block device for writing." Since that's what it actually does, right? --D > > + 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 >