On Tue, 2020-11-24 at 14:33 -0600, Benjamin Marzinski wrote: > On Fri, Nov 06, 2020 at 06:32:16PM +0100, Martin Wilck wrote: > > On Thu, 2020-11-05 at 18:41 -0600, Benjamin Marzinski wrote: > > > I can't make this segfault. So that looks good, but it does need > > > libmultipath.version updated to include checker_thread_entry() > > > > Great news, thanks. Well the library version stuff hasn't been > > committed yet anyway, this was against Christophe's current base. > > Actually, I ran into a different segfault with this patch. > > While the tur checker's libcheck_check() function is run under > locking, > so the device cannot be removed, The thread it creates is not. This > means that it is possible for the device to get removed after > libcheck_check() runs, but before checker_thread_entry() runs. In > this > case, when checker_thread_entry() is finally run, the passed in > checker > structure would already have been freed, causing a segfault. I have > been able to easily reproduce this in the case where multipath device > creation failed in the kernel. > > I'm pretty sure that the checker class needs its ref count increased > before the thread is created, and the thread inself must only access > the > context, which should include a pointer to the class. > Thanks for pointing this out. I'll have another look. Martin -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
