diff mbox series

[4.19,72/84] pkt_sched: fq: do not accept silly TCA_FQ_QUANTUM

Message ID 20200111094911.672249132@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH Jan. 11, 2020, 9:50 a.m. UTC 
From: Eric Dumazet <edumazet@google.com>

[ Upstream commit d9e15a2733067c9328fb56d98fe8e574fa19ec31 ]

As diagnosed by Florian :

If TCA_FQ_QUANTUM is set to 0x80000000, fq_deueue()
can loop forever in :

if (f->credit <= 0) {
  f->credit += q->quantum;
  goto begin;
}

... because f->credit is either 0 or -2147483648.

Let's limit TCA_FQ_QUANTUM to no more than 1 << 20 :
This max value should limit risks of breaking user setups
while fixing this bug.

Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Diagnosed-by: Florian Westphal <fw@strlen.de>
Reported-by: syzbot+dc9071cc5a85950bdfce@syzkaller.appspotmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sched/sch_fq.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
diff mbox series

Patch

--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -735,10 +735,12 @@  static int fq_change(struct Qdisc *sch,
 	if (tb[TCA_FQ_QUANTUM]) {
 		u32 quantum = nla_get_u32(tb[TCA_FQ_QUANTUM]);
 
-		if (quantum > 0)
+		if (quantum > 0 && quantum <= (1 << 20)) {
 			q->quantum = quantum;
-		else
+		} else {
+			NL_SET_ERR_MSG_MOD(extack, "invalid quantum");
 			err = -EINVAL;
+		}
 	}
 
 	if (tb[TCA_FQ_INITIAL_QUANTUM])