Mon, Jul 29, 2019 at 10:00:18AM CEST, [email protected] wrote: >In dequeue_func(), there is an if statement on line 74 to check whether >skb is NULL: > if (skb) > >When skb is NULL, it is used on line 77: > prefetch(&skb->end); > >Thus, a possible null-pointer dereference may occur. > >To fix this bug, skb->end is used when skb is not NULL. > >This bug is found by a static analysis tool STCheck written by us. > >Fixes: 79bdc4c862af ("codel: generalize the implementation")
Looks like this is something being there since the beginning: commit 76e3cc126bb223013a6b9a0e2a51238d1ef2e409 Author: Eric Dumazet <[email protected]> Date: Thu May 10 07:51:25 2012 +0000 codel: Controlled Delay AQM Please adjust "Fixes:". The fix itself looks fine to me. Reviewed-by: Jiri Pirko <[email protected]> >Signed-off-by: Jia-Ju Bai <[email protected]> >--- >v2: >* Add a fix tag. > Thank Jiri Pirko for helpful advice. > >--- > net/sched/sch_codel.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > >diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c >index 25ef172c23df..30169b3adbbb 100644 >--- a/net/sched/sch_codel.c >+++ b/net/sched/sch_codel.c >@@ -71,10 +71,10 @@ static struct sk_buff *dequeue_func(struct codel_vars >*vars, void *ctx) > struct Qdisc *sch = ctx; > struct sk_buff *skb = __qdisc_dequeue_head(&sch->q); > >- if (skb) >+ if (skb) { > sch->qstats.backlog -= qdisc_pkt_len(skb); >- >- prefetch(&skb->end); /* we'll need skb_shinfo() */ >+ prefetch(&skb->end); /* we'll need skb_shinfo() */ >+ } > return skb; > } > >-- >2.17.0 >
