Re: [PATCH net] net: sched: replaced invalid qdisc tree flush helper in qdisc_replace
From: Jakub Kicinski <kuba@kernel.org>
Date: 2021-01-28 21:33:24
On Wed, 27 Jan 2021 00:56:41 +0300 Alexander Ovechkin wrote:
Commit e5f0e8f8e456 ("net: sched: introduce and use qdisc tree flush/purge helpers")
introduced qdisc tree flush/purge helpers, but erroneously used flush helper
instead of purge helper in qdisc_replace function.
This issue was found in our CI, that tests various qdisc setups by configuring
qdisc and sending data through it. Call of invalid helper sporadically leads
to corruption of vt_tree/cf_tree of hfsc_class that causes kernel oops:The patch in question indeed does change the code, but I wonder if the problem isn't in HFSC. Why would the caller depend on the old qdisc being purged by qdisc_replace()? Please add some more info on this..
Fixes: e5f0e8f8e456 ("net: sched: introduce and use qdisc tree flush/purge
helpers")... fix the tag (it shouldn't be wrapped), and CC the right people (especially the author of the patch you're pointing the tag at - scripts/get_maintainer is your friend), and repost.
quoted hunk ↗ jump to hunk
Signed-off-by: Alexander Ovechkin <redacted> Reported-by: Alexander Kuznetsov <redacted> Acked-by: Dmitry Monakhov <redacted> Acked-by: Dmitry Yakunin <redacted> --- include/net/sch_generic.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 639e465a108f..5b490b5591df 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h@@ -1143,7 +1143,7 @@ static inline struct Qdisc *qdisc_replace(struct Qdisc *sch, struct Qdisc *new, old = *pold; *pold = new; if (old != NULL) - qdisc_tree_flush_backlog(old); + qdisc_purge_queue(old); sch_tree_unlock(sch); return old;