Date: Wed, 15 Jun 2011 18:42:45 +0400 From: Solar Designer <solar@...nwall.com> To: kernel-hardening@...ts.openwall.com Subject: Re: destroy unused shmem segments Vasiliy, On Tue, Jun 14, 2011 at 12:33:45PM +0400, Vasiliy Kulikov wrote: > It is used in case shmem segment was created, but never used. In this > case refcount is never incremented and never decremented, shm_clone() > isn't called. > > If shmctl() sets IPC_RMID, it is deleted, but as you have implemented > implicit semantics (like IPC_RMID is always set), actual check in > shmget()+exit() is needed. > > Spotted by reading -ow README and testing :) Oh, right. Having documentation is good. > I think forcing IPC_RMID should be configurable via sysctl like other > ipc variables. Something like /proc/sys/kernel/shm_orphans_denied. > And I think changing it from 0 to 1 should destroy already orphaned > segments without users. OK. Thanks, Alexander
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