Messages in this thread | | | Date | Tue, 14 Jan 2014 21:13:11 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/2] sys, seccomp: add PR_SECCOMP_EXT and SECCOMP_EXT_ACT_TSYNC |
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On 01/14, Oleg Nesterov wrote: > > On 01/14, Oleg Nesterov wrote: > > > > > + get_seccomp_filter(caller); > > > + /* > > > + * Drop the task reference to the shared ancestor since > > > + * current's path will hold a reference. (This also > > > + * allows a put before the assignment.) > > > + */ > > > + put_seccomp_filter(thread); > > > + thread->seccomp.filter = caller->seccomp.filter; > > > > As I said, I do not understand this patch yet, but this looks suspicious. > > > > Why we can't race with this thread doing clone(CLONE_THREAD) ? We do > > not the the new thread yet, but its ->seccomp can be already copied > > by copy_process(), no? > > And it seems that this can obviously race with seccomp_attach_filter() > called by this "thread".
Heh. I just noticed that this patch is not first in series, and I wasn't cc'ed. I found this one on marc.info,
http://marc.info/?l=linux-kernel&m=138964557211277
this explains task_lock(). But this can't fix the race with copy_process, and the patch itself doesn't look right... if nothing else, we can't do copy_from_user() under task_lock().
Oleg.
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