On Sun, 2006-02-19 at 15:35 +0100, Klaus Schmidinger wrote:
Ville Skyttä wrote:
On Thu, 2006-02-16 at 20:01 +0100, leo2@pec.homeip.net wrote:
The current function to activate core-dumps for vdr running setuid ist only working for kernel > 2.6.13 ( says the comment in vdr.c ). Actualy it is not working for 2.4.21 but it was easy an easy change, just replace prctl(PR_SET_DUMPABLE, 2, 0, 0, 0) with prctl(PR_SET_DUMPABLE, 1, 0, 0, 0)
If you need the switch with "2" ( what does "2" mean for >2.6.13 ??)
It's "2" intentionally. "1" is a "no security" mode, "2" makes the core dumps readable by root only and applies additional checks. Like the comment says, "2" is available in kernels >= 2.6.13 only. For more info, see eg. the suid_dumpable description here: http://marc.theaimsgroup.com/?l=linux-kernel&m=109647550421014&w=2
Yes, the net effect is that the unmodified VDR 1.3.42 won't produce core dumps at all when not running as root with < 2.6.13 kernels, but IMO that's a reasonable tradeoff, at least as far as the default is concerned.
So does this mean that '1' would work on older kernels?
For some values of "work", yes ;)
Would it be feasible to use just '1' - after all, there's not much security about a VDR core file.
Well, the above link contains descriptions about what 1 means. The documentation says "... no security is applied. This is intended for system debugging situations only." whereas for 2 they say "... attempting to debug problems in a normal environment". Note that it's not only about the file permissions or the core file's contents. Only 2 opens the dump file with O_EXCL. Both 1 and 2 seem to use O_NOFOLLOW though.