geli(8) breaks after a couple hours of uptime
Pawel Jakub Dawidek
pjd at FreeBSD.org
Sat Feb 9 23:34:15 UTC 2013
On Sat, Feb 09, 2013 at 06:00:53PM +0200, Andriy Gapon wrote:
> on 09/02/2013 17:04 Andrey Zonov said the following:
> > On 2/9/13 5:07 PM, Fabian Keil wrote:
> >> This would at least prevent the segfault.
> > I see two possibilities to get segfault:
> > - no checking for result from memory allocation functions
> > - too big stack
> > I have no found any broken memory allocation checking, but I found two
> > big objects on the stack. One is buf[MAXPHYS] in eli_genkey_files() and
> > another is passbuf[MAXPHYS] in eli_genkey_passphrase(). If we change
> > these two to malloc(), then we can handle error from malloc(), print
> > some useful message and prevent segfault.
> I'd rather do what Kostik suggested and Fabian mentioned: instead of
> mlockall(MCL_FUTURE) the code should mlock only the (explicitly designated)
> buffers that can contain sensitive data.
geli(8) almost exclusively deals with sensitive data. Even mlocking
MAXPHYS would fail with current limits, but this is bad idea.
With mlockall() I am sure I didn't miss anything - be it forgetting
about mlocking some buffer or zeroing it before munlock. I'm also sure
someone else who can modify geli(8) in the future won't miss anything
geli(8) is relatively simple program, it doesn't allocate megabytes of
memory for different pruposes and just needs few pages for sensitive
data. As I said most of the memory it uses is for sensitive data.
The obvious problem is allocating MAXPHYS on the stack. This has to be
changed, especially that we may want to rise MAXPHYS in the future.
Other than that I expect thing would be tuned properly so that geli(8)
can work by default. I'm happy to use smaller buffers than MAXPHYS -
keyfiles are far smaller usually than 128kB, so there shouldn't be any
issue with this.
Pawel Jakub Dawidek http://www.wheelsystems.com
FreeBSD committer http://www.FreeBSD.org
Am I Evil? Yes, I Am! http://tupytaj.pl
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