On 23/08/2024 14:05, Darrick J. Wong wrote: > On Fri, Aug 23, 2024 at 09:11:22AM -0700, Bart Van Assche wrote: >> On 8/23/24 7:26 AM, Guilherme G. Piccoli wrote: >>> + 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 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. >>> + >> >> Does this flag also affect direct I/O? If so, does this mean that the >> reference to the page cache should be left out? > > I think it does affect directio, since the validation is done at open > time via bdev_may_open, right? > Indeed, good point! It does affect direct I/O, I've just tested in 6.11-rc3 using dd (with and w/o oflags=direct), same result. I'll resend, dropping the mention to page cache - thanks! Guilherme
