On Mon, Aug 19, 2024 at 07:56:27PM -0300, 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. > > Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx> > --- > 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. 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 > + > bert_disable [ACPI] > Disable BERT OS support on buggy BIOSes. > > -- > 2.45.2 > >