Messages in this thread | | | Date | Tue, 8 Aug 2006 17:34:35 +0200 | From | Björn Steinbrink <> | Subject | Re: [PATCH] sys_getppid oopses on debug kernel |
| |
On 2006.08.08 08:26:57 -0700, Dave Hansen wrote: > On Tue, 2006-08-08 at 14:22 +0400, Kirill Korotaev wrote: > > sys_getppid() optimization can access a freed memory. > > On kernels with DEBUG_SLAB turned ON, this results in > > Oops. > ... > > +#else > > + /* > > + * ->real_parent could be released before dereference and > > + * we accessed freed kernel memory, which faults with debugging on. > > + * Keep it simple and stupid. > > + */ > > + read_lock(&tasklist_lock); > > + pid = current->group_leader->real_parent->tgid; > > + read_unlock(&tasklist_lock); > > +#endif > > return pid; > > } > > Accessing freed memory is a bug, always, not just *only* when slab > debugging is on, right? Doesn't this mean we could get junk, or that > the reader could potentially run off a bad pointer? > > It seems that this patch only papers over the problem in the case when > it is observed, but doesn't really even fix the normal case. > > Could we use a seqlock to determine when real_parent is in flux, and > re-read real_parent until we get a consistent one? We could use in in > lieu of the existing for() loop.
See this thread: http://lkml.org/lkml/2006/8/8/215
Björn - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |