Strange IO performance with UFS

Konstantin Belousov kostikbel at gmail.com
Sat Jul 5 18:06:05 UTC 2014


On Sat, Jul 05, 2014 at 10:24:23PM +0800, Julian Elischer wrote:
> On 7/5/14, 7:24 PM, Konstantin Belousov wrote:
> > This leaves the unwritten portion of the block with the garbage. I
> > believe that it is not harmful, since the only way for usermode to
> > access that garbage is through the mmap(2). The vnode_generic_getpages()
> > zeroes out parts of the page which are after EOF.
> 
> I have vague memories of this being in a security bulletin once along 
> the lines of "random data disclosure"  by making tons of 1 frag size 
> files and then mmapping them.
I am not sure what do you reference there.

Might be,
http://www.freebsd.org/security/advisories/FreeBSD-SA-13:11.sendfile.asc ?
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