| Message ID | 20190729080018.28678-1-baijiaju1990@gmail.com |
|---|---|
| State | Superseded |
| Delegated to: | David Miller |
| Headers | show |
| Series | [v2] net: sched: Fix a possible null-pointer dereference in dequeue_func() | expand |
Mon, Jul 29, 2019 at 10:00:18AM CEST, baijiaju1990@gmail.com 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 <edumazet@google.com> 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 <jiri@mellanox.com> >Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com> >--- >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 >
On 2019/7/29 16:18, Jiri Pirko wrote: > Mon, Jul 29, 2019 at 10:00:18AM CEST, baijiaju1990@gmail.com 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 <edumazet@google.com> > Date: Thu May 10 07:51:25 2012 +0000 > > codel: Controlled Delay AQM > > > Please adjust "Fixes:". Thanks for the advice :) I have sent a v3 patch. Best wishes, Jia-Ju Bai
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; }
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") Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com> --- v2: * Add a fix tag. Thank Jiri Pirko for helpful advice. --- net/sched/sch_codel.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)