Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx> writes: > On Wed, 22 Jan 2020, Jouni Högander wrote: > >> Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> writes: >> >> > Now queued up, I'll push out -rc2 versions with this fix. >> >> > >> >> > greg k-h >> >> >> >> We have also been informed about another regression these two commits >> >> are causing: >> >> >> >> https://lore.kernel.org/lkml/ace19af4-7cae-babd-bac5-cd3505dcd874@xxxxxxxxxxxxxxxxxxx/ >> >> >> >> I suggest to drop these two patches from this queue, and give us a >> >> week to shake out the regressions of the change, and once ready, we >> >> can include the complete set of fixes to stable (probably in a week or >> >> two). >> > >> > Ok, thanks for the information, I've now dropped them from all of the >> > queues that had them in them. >> > >> > greg k-h >> >> I have now run more extensive Syzkaller testing on following patches: >> >> cb626bf566eb net-sysfs: Fix reference count leak >> ddd9b5e3e765 net-sysfs: Call dev_hold always in rx_queue_add_kobject >> e0b60903b434 net-sysfs: Call dev_hold always in netdev_queue_add_kobje >> 48a322b6f996 net-sysfs: fix netdev_queue_add_kobject() breakage >> b8eb718348b8 net-sysfs: Fix reference count leak in rx|netdev_queue_add_kobject >> >> These patches are fixing couple of memory leaks including this one found >> by Syzbot: https://syzkaller.appspot.com/bug?extid=ad8ca40ecd77896d51e2 >> >> I can reproduce these memory leaks in following stable branches: 4.14, >> 4.19, and 5.4. >> >> These are all now merged into net/master tree and based on my testing >> they are ready to be taken into stable branches as well. >> > > + syzkaller list > Jouni et. al, please drop Linus in further responses; Linus, it was wrong > to add you to this thread in the first place (reason is explained below) > > Jouni, thanks for investigating. > > It raises the following questions and comments: > > - Does the memory leak NOT appear on 4.9 and earlier LTS branches (or did > you not check that)? If it does not appear, can you bisect it with the > reproducer to the commit between 4.14 and 4.9? I tested and these memory leaks are not reproucible in 4.9 and earlier. > > - Do the reproducers you found with your syzkaller testing show the same > behaviour (same bisection) as the reproducers from syzbot? Yes, they are same. > > - I fear syzbot's automatic bisection on is wrong, and Linus' commit > 0e034f5c4bc4 ("iwlwifi: fix mis-merge that breaks the driver") is not to > blame here; that commit did not cause the memory leak, but fixed some > unrelated issue that simply confuses syzbot's automatic bisection. > > Just FYI: Dmitry Vyukov's evaluation of the syzbot bisection shows that > about 50% are wrong, e.g., due to multiple bugs being triggered with one > reproducer and the difficulty of automatically identifying them of being > different due to different root causes (despite the smart heuristics of > syzkaller & syzbot). So, to identify the actual commit on which the memory > leak first appeared, you need to bisect manually with your own judgement > if the reported bug stack trace fits to the issue you investigating. Or > you use syzbot's automatic bisection but then with a reduced kernel config > that cannot be confused by other issues. You might possibly also hit a > "beginning of time" in your bisection, where KASAN was simply not > supported, then the initially causing commit can simply not determined by > bisection with the reproducer and needs some code inspection and > archaeology with git. Can you go ahead try to identify the correct commit > for this issue? These two commits (that are not in 4.9 and earlier) are intorducing these leaks: commit e331c9066901dfe40bea4647521b86e9fb9901bb Author: YueHaibing <yuehaibing@xxxxxxxxxx> Date: Tue Mar 19 10:16:53 2019 +0800 net-sysfs: call dev_hold if kobject_init_and_add success [ Upstream commit a3e23f719f5c4a38ffb3d30c8d7632a4ed8ccd9e ] In netdev_queue_add_kobject and rx_queue_add_kobject, if sysfs_create_group failed, kobject_put will call netdev_queue_release to decrease dev refcont, however dev_hold has not be called. So we will see this while unregistering dev: unregister_netdevice: waiting for bcsh0 to become free. Usage count = -1 Reported-by: Hulk Robot <hulkci@xxxxxxxxxx> Fixes: d0d668371679 ("net: don't decrement kobj reference count on init fail ure") Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> commit d0d6683716791b2a2761a1bb025c613eb73da6c3 Author: stephen hemminger <stephen@xxxxxxxxxxxxxxxxxx> Date: Fri Aug 18 13:46:19 2017 -0700 net: don't decrement kobj reference count on init failure If kobject_init_and_add failed, then the failure path would decrement the reference count of the queue kobject whose reference count was already zero. Fixes: 114cf5802165 ("bql: Byte queue limits") Signed-off-by: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> > > > Lukas BR, Jouni Högander
