On Sat, Sep 7, 2013 at 9:54 PM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote: > On Sun, Sep 08, 2013 at 02:37:03PM +1000, Herbert Xu wrote: >> On Sat, Sep 07, 2013 at 08:34:15PM -0700, Kees Cook wrote: >> > >> > However, I noticed on the "good" path (even without the above patch), >> > I sometimes see a double-kfree triggered by the modprobe process. I >> > can't, however, see how that's happening, since larval_destroy should >> > only be called when refcnt == 0. >> >> Do you still see this double free with this patch? Without the >> patch it is completely expected as killing the same lavral twice >> will cause memory corruption leading to all sorts of weirdness, >> even if you stop it from deleting the list entry twice. I noticed while testing the larval_kill fix, and then tried it again after reverting the fix -- both showed the behavior. > Actually I know what it is. sha512 registers two algorithms. > Therefore, it will create two larvals in sequence and then destroy > them in turn. So it's not a double free at all. If you put a > printk in crypto_larval_alloc that should confirm this. Ah! That would make sense; it just happens to re-allocate to the exact same location, yes. Whew, that's certainly what's happening. I can retest to confirm in my morning. Thanks again for the larval_kill fix! I'll get it rolled out for wider testing to confirm that it make our crash numbers go down. -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
