On Thu, 2009-07-30 at 10:29 +0000, Carlo Marcelo Arenas Belon wrote: > On Wed, Jul 29, 2009 at 03:42:05PM -0400, Jason A. Smith wrote: > > > > In gmond, the monitor-core/libmetrics/linux/metrics.c:find_disk_space() > > function, was not only using small character arrays, but the arrays for > > the sscanf after the fgets were smaller than the array for the line it > > just read in, which can lead to buffer overflows and the "stack > > smashing" problem that we were having. > > using fixed size arrays in the stack is never a good idea. > in this case it could be theoretically possible to exploit this overflow > with the help of a malicious NFS server (very unlikely though). > > > To fix out problem and prevent the overflows, I made a patch to increase > > the size of the arrays and also make each of the arrays used in the > > sscanf the same size as the line buffer used in fgets, so there is no > > chance of another overflow. > > committed for trunk in r2007, but the new implementation might also > generate segfaults on its own due to stack overflows when running with > very small stacks as it requires a bigger stack. > > IMHO it would be better to migrate this function to use getmntent and > friends as it was done already for Cygwin, Solaris and the BSD and that > way avoid the use of local buffers and parsing of the /proc/mounts file > directly.
Hi Carlo, This is a good idea, I didn't think to check the libmetric code from the other OSes. Besides a few minor differences for the remote_mounts & valid_mount_type functions and the seen_before part, the solaris & linux code look almost identical. Should the linux code be updated to look more like the solaris code? Too bad it isn't possible to merge similar code instead copying it. ~Jason -- /------------------------------------------------------------------\ | Jason A. Smith Email: smit...@bnl.gov | | Atlas Computing Facility, Bldg. 510M Phone: +1-631-344-4226 | | Brookhaven National Lab, P.O. Box 5000 Fax: +1-631-344-7616 | | Upton, NY 11973-5000, U.S.A. | \------------------------------------------------------------------/
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