| Message ID | 20221031060835.11722-1-yin31149@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net: sched: fix memory leak in tcindex_set_parms | expand |
On Mon, 31 Oct 2022 14:08:35 +0800 Hawkins Jiawei wrote: > Kernel will uses tcindex_change() to change an existing s/will// > traffic-control-indices filter properties. During the > process of changing, kernel will clears the old s/will// > traffic-control-indices filter result, and updates it > by RCU assigning new traffic-control-indices data. > > Yet the problem is that, kernel will clears the old s/will// > traffic-control-indices filter result, without destroying > its tcf_exts structure, which triggers the above > memory leak. > > This patch solves it by using tcf_exts_destroy() to > destroy the tcf_exts structure in old > traffic-control-indices filter result. > Please provide a Fixes tag to where the problem was introduced (or the initial git commit). > Link: https://lore.kernel.org/all/0000000000001de5c505ebc9ec59@google.com/ > Reported-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com > Tested-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com > Signed-off-by: Hawkins Jiawei <yin31149@gmail.com> > --- > net/sched/cls_tcindex.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c > index 1c9eeb98d826..dc872a794337 100644 > --- a/net/sched/cls_tcindex.c > +++ b/net/sched/cls_tcindex.c > @@ -338,6 +338,9 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > struct tcf_result cr = {}; > int err, balloc = 0; > struct tcf_exts e; > +#ifdef CONFIG_NET_CLS_ACT > + struct tcf_exts old_e = {}; > +#endif Why all the ifdefs? > err = tcf_exts_init(&e, net, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE); > if (err < 0) > @@ -479,6 +482,14 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > } > > if (old_r && old_r != r) { > +#ifdef CONFIG_NET_CLS_ACT > + /* r->exts is not copied from old_r->exts, and > + * the following code will clears the old_r, so > + * we need to destroy it after updating the tp->root, > + * to avoid memory leak bug. > + */ > + old_e = old_r->exts; > +#endif Can't you localize all the changes to this if block? Maybe add a function called tcindex_filter_result_reinit() which will act more appropriately? > err = tcindex_filter_result_init(old_r, cp, net); > if (err < 0) { > kfree(f); > @@ -510,6 +521,9 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > tcf_exts_destroy(&new_filter_result.exts); > } > > +#ifdef CONFIG_NET_CLS_ACT > + tcf_exts_destroy(&old_e); > +#endif > if (oldp) > tcf_queue_work(&oldp->rwork, tcindex_partial_destroy_work); > return 0;
Hi Jakub, On Thu, 3 Nov 2022 at 11:26, Jakub Kicinski <kuba@kernel.org> wrote: > > On Mon, 31 Oct 2022 14:08:35 +0800 Hawkins Jiawei wrote: > > Kernel will uses tcindex_change() to change an existing > > s/will// > > > traffic-control-indices filter properties. During the > > process of changing, kernel will clears the old > > s/will// > > > traffic-control-indices filter result, and updates it > > by RCU assigning new traffic-control-indices data. > > > > Yet the problem is that, kernel will clears the old > > s/will// Thanks for the suggestion. I will amend these in the v2 patch. > > > traffic-control-indices filter result, without destroying > > its tcf_exts structure, which triggers the above > > memory leak. > > > > This patch solves it by using tcf_exts_destroy() to > > destroy the tcf_exts structure in old > > traffic-control-indices filter result. > > > > Please provide a Fixes tag to where the problem was introduced > (or the initial git commit). Thanks for reminding, it seems that the problem was introduced by commit b9a24bb76bf6 ("net_sched: properly handle failure case of tcf_exts_init()"), because it was in this commit that kernel allocated the struct tcf_exts for new traffic-control-indices filter result in tcindex_alloc_perfect_hash(). I will add the tag in the v2 patch. > > > Link: https://lore.kernel.org/all/0000000000001de5c505ebc9ec59@google.com/ > > Reported-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com > > Tested-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com > > Signed-off-by: Hawkins Jiawei <yin31149@gmail.com> > > --- > > net/sched/cls_tcindex.c | 14 ++++++++++++++ > > 1 file changed, 14 insertions(+) > > > > diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c > > index 1c9eeb98d826..dc872a794337 100644 > > --- a/net/sched/cls_tcindex.c > > +++ b/net/sched/cls_tcindex.c > > @@ -338,6 +338,9 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > > struct tcf_result cr = {}; > > int err, balloc = 0; > > struct tcf_exts e; > > +#ifdef CONFIG_NET_CLS_ACT > > + struct tcf_exts old_e = {}; > > +#endif > > Why all the ifdefs? Thanks for suggestion, it seems that these ifdefs are not needed. I will delete these in the v2 patch. > > > err = tcf_exts_init(&e, net, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE); > > if (err < 0) > > @@ -479,6 +482,14 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > > } > > > > if (old_r && old_r != r) { > > +#ifdef CONFIG_NET_CLS_ACT > > + /* r->exts is not copied from old_r->exts, and > > + * the following code will clears the old_r, so > > + * we need to destroy it after updating the tp->root, > > + * to avoid memory leak bug. > > + */ > > + old_e = old_r->exts; > > +#endif > > Can't you localize all the changes to this if block? > > Maybe add a function called tcindex_filter_result_reinit() > which will act more appropriately? I think we shouldn't put the tcf_exts_destroy(&old_e) into this if block, or other RCU readers may derefer the freed memory (Please correct me If I am wrong). So I put the tcf_exts_destroy(&old_e) near the tcindex destroy work, after the RCU updateing. > > > err = tcindex_filter_result_init(old_r, cp, net); > > if (err < 0) { > > kfree(f); > > @@ -510,6 +521,9 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > > tcf_exts_destroy(&new_filter_result.exts); > > } > > > > +#ifdef CONFIG_NET_CLS_ACT > > + tcf_exts_destroy(&old_e); > > +#endif > > if (oldp) > > tcf_queue_work(&oldp->rwork, tcindex_partial_destroy_work); > > return 0;
On Fri, 4 Nov 2022 00:07:00 +0800 Hawkins Jiawei wrote: > > Can't you localize all the changes to this if block? > > > > Maybe add a function called tcindex_filter_result_reinit() > > which will act more appropriately? > > I think we shouldn't put the tcf_exts_destroy(&old_e) > into this if block, or other RCU readers may derefer the > freed memory (Please correct me If I am wrong). > > So I put the tcf_exts_destroy(&old_e) near the tcindex > destroy work, after the RCU updateing. I'm not sure what this code is trying to do, to be honest. Your concern that there may be a concurrent reader is valid, but then again tcindex_filter_result_init() just wipes the entire structure with a memset() so concurrent readers are already likely broken? Maybe tcindex_filter_result_init() dates back to times when exts were a list (see commit 22dc13c837c) and calling tcf_exts_init() wasn't that different than cleaning it up? In other words this code is trying to destroy old_r, not reinitialize it? > > > > > err = tcindex_filter_result_init(old_r, cp, net);
On Fri, 4 Nov 2022 at 10:23, Jakub Kicinski <kuba@kernel.org> wrote: > > On Fri, 4 Nov 2022 00:07:00 +0800 Hawkins Jiawei wrote: > > > Can't you localize all the changes to this if block? > > > > > > Maybe add a function called tcindex_filter_result_reinit() > > > which will act more appropriately? > > > > I think we shouldn't put the tcf_exts_destroy(&old_e) > > into this if block, or other RCU readers may derefer the > > freed memory (Please correct me If I am wrong). > > > > So I put the tcf_exts_destroy(&old_e) near the tcindex > > destroy work, after the RCU updateing. > > I'm not sure what this code is trying to do, to be honest. > Your concern that there may be a concurrent reader is valid, > but then again tcindex_filter_result_init() just wipes the > entire structure with a memset() so concurrent readers are > already likely broken? > > Maybe tcindex_filter_result_init() dates back to times when > exts were a list (see commit 22dc13c837c) and calling > tcf_exts_init() wasn't that different than cleaning it up? > In other words this code is trying to destroy old_r, not > reinitialize it? Yes, I also think this code is just trying to destroy the old_r. In my opinion, the context here is a bit like, this filter's some properties has been changed, so kernel should drop its old filter result and update a new one. Before kernel finishes RCU updating, concurrent readers should see an empty result(or a valid old result), cleaned by tcindex_filter_result_init(). This won't trigger the memory leak before commit b9a24bb76bf6 ("net_sched: properly handle failure case of tcf_exts_init()"), I think. Because the new filter result still uses the old_r->exts. Yet after this commit, kernel allocates the new struct tcf_exts for new filter result in tcindex_alloc_perfect_hash(), which triggers the memory leak if kernel cleans the old_r without destroying its newly allocted struct tcf_exts. As for the patch, I think we'd better free this struct tcf_exts after RCU updating, to make sure that concurrent readers can only see an empty result or a valid old result, before finishing updating (Please correct me if I am wrong). > > > > > > > > err = tcindex_filter_result_init(old_r, cp, net);
On Mon, Oct 31, 2022 at 02:08:35PM +0800, Hawkins Jiawei wrote: > Syzkaller reports a memory leak as follows: > ==================================== > BUG: memory leak > unreferenced object 0xffff88810c287f00 (size 256): > comm "syz-executor105", pid 3600, jiffies 4294943292 (age 12.990s) > hex dump (first 32 bytes): > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > backtrace: > [<ffffffff814cf9f0>] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046 > [<ffffffff839c9e07>] kmalloc include/linux/slab.h:576 [inline] > [<ffffffff839c9e07>] kmalloc_array include/linux/slab.h:627 [inline] > [<ffffffff839c9e07>] kcalloc include/linux/slab.h:659 [inline] > [<ffffffff839c9e07>] tcf_exts_init include/net/pkt_cls.h:250 [inline] > [<ffffffff839c9e07>] tcindex_set_parms+0xa7/0xbe0 net/sched/cls_tcindex.c:342 > [<ffffffff839caa1f>] tcindex_change+0xdf/0x120 net/sched/cls_tcindex.c:553 > [<ffffffff8394db62>] tc_new_tfilter+0x4f2/0x1100 net/sched/cls_api.c:2147 > [<ffffffff8389e91c>] rtnetlink_rcv_msg+0x4dc/0x5d0 net/core/rtnetlink.c:6082 > [<ffffffff839eba67>] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2540 > [<ffffffff839eab87>] netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] > [<ffffffff839eab87>] netlink_unicast+0x397/0x4c0 net/netlink/af_netlink.c:1345 > [<ffffffff839eb046>] netlink_sendmsg+0x396/0x710 net/netlink/af_netlink.c:1921 > [<ffffffff8383e796>] sock_sendmsg_nosec net/socket.c:714 [inline] > [<ffffffff8383e796>] sock_sendmsg+0x56/0x80 net/socket.c:734 > [<ffffffff8383eb08>] ____sys_sendmsg+0x178/0x410 net/socket.c:2482 > [<ffffffff83843678>] ___sys_sendmsg+0xa8/0x110 net/socket.c:2536 > [<ffffffff838439c5>] __sys_sendmmsg+0x105/0x330 net/socket.c:2622 > [<ffffffff83843c14>] __do_sys_sendmmsg net/socket.c:2651 [inline] > [<ffffffff83843c14>] __se_sys_sendmmsg net/socket.c:2648 [inline] > [<ffffffff83843c14>] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2648 > [<ffffffff84605fd5>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] > [<ffffffff84605fd5>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > [<ffffffff84800087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd > ==================================== > > Kernel will uses tcindex_change() to change an existing > traffic-control-indices filter properties. During the > process of changing, kernel will clears the old > traffic-control-indices filter result, and updates it > by RCU assigning new traffic-control-indices data. > > Yet the problem is that, kernel will clears the old > traffic-control-indices filter result, without destroying > its tcf_exts structure, which triggers the above > memory leak. > > This patch solves it by using tcf_exts_destroy() to > destroy the tcf_exts structure in old > traffic-control-indices filter result. So... your patch can be just the following one-liner, right? diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c index 1c9eeb98d826..00a6c04a4b42 100644 --- a/net/sched/cls_tcindex.c +++ b/net/sched/cls_tcindex.c @@ -479,6 +479,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, } if (old_r && old_r != r) { + tcf_exts_destroy(&old_r->exts); err = tcindex_filter_result_init(old_r, cp, net); if (err < 0) { kfree(f);
Hi Cong, On Sun, 6 Nov 2022 at 03:50, Cong Wang <xiyou.wangcong@gmail.com> wrote: > > On Mon, Oct 31, 2022 at 02:08:35PM +0800, Hawkins Jiawei wrote: > > Syzkaller reports a memory leak as follows: > > ==================================== > > BUG: memory leak > > unreferenced object 0xffff88810c287f00 (size 256): > > comm "syz-executor105", pid 3600, jiffies 4294943292 (age 12.990s) > > hex dump (first 32 bytes): > > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > backtrace: > > [<ffffffff814cf9f0>] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046 > > [<ffffffff839c9e07>] kmalloc include/linux/slab.h:576 [inline] > > [<ffffffff839c9e07>] kmalloc_array include/linux/slab.h:627 [inline] > > [<ffffffff839c9e07>] kcalloc include/linux/slab.h:659 [inline] > > [<ffffffff839c9e07>] tcf_exts_init include/net/pkt_cls.h:250 [inline] > > [<ffffffff839c9e07>] tcindex_set_parms+0xa7/0xbe0 net/sched/cls_tcindex.c:342 > > [<ffffffff839caa1f>] tcindex_change+0xdf/0x120 net/sched/cls_tcindex.c:553 > > [<ffffffff8394db62>] tc_new_tfilter+0x4f2/0x1100 net/sched/cls_api.c:2147 > > [<ffffffff8389e91c>] rtnetlink_rcv_msg+0x4dc/0x5d0 net/core/rtnetlink.c:6082 > > [<ffffffff839eba67>] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2540 > > [<ffffffff839eab87>] netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] > > [<ffffffff839eab87>] netlink_unicast+0x397/0x4c0 net/netlink/af_netlink.c:1345 > > [<ffffffff839eb046>] netlink_sendmsg+0x396/0x710 net/netlink/af_netlink.c:1921 > > [<ffffffff8383e796>] sock_sendmsg_nosec net/socket.c:714 [inline] > > [<ffffffff8383e796>] sock_sendmsg+0x56/0x80 net/socket.c:734 > > [<ffffffff8383eb08>] ____sys_sendmsg+0x178/0x410 net/socket.c:2482 > > [<ffffffff83843678>] ___sys_sendmsg+0xa8/0x110 net/socket.c:2536 > > [<ffffffff838439c5>] __sys_sendmmsg+0x105/0x330 net/socket.c:2622 > > [<ffffffff83843c14>] __do_sys_sendmmsg net/socket.c:2651 [inline] > > [<ffffffff83843c14>] __se_sys_sendmmsg net/socket.c:2648 [inline] > > [<ffffffff83843c14>] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2648 > > [<ffffffff84605fd5>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > [<ffffffff84605fd5>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > > [<ffffffff84800087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd > > ==================================== > > > > Kernel will uses tcindex_change() to change an existing > > traffic-control-indices filter properties. During the > > process of changing, kernel will clears the old > > traffic-control-indices filter result, and updates it > > by RCU assigning new traffic-control-indices data. > > > > Yet the problem is that, kernel will clears the old > > traffic-control-indices filter result, without destroying > > its tcf_exts structure, which triggers the above > > memory leak. > > > > This patch solves it by using tcf_exts_destroy() to > > destroy the tcf_exts structure in old > > traffic-control-indices filter result. > > So... your patch can be just the following one-liner, right? Yes, as you and Jakub points out, all ifdefs can be removed, and I will refactor those in v2 patch. > > > diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c > index 1c9eeb98d826..00a6c04a4b42 100644 > --- a/net/sched/cls_tcindex.c > +++ b/net/sched/cls_tcindex.c > @@ -479,6 +479,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > } > > if (old_r && old_r != r) { > + tcf_exts_destroy(&old_r->exts); > err = tcindex_filter_result_init(old_r, cp, net); > if (err < 0) { > kfree(f); As for the position of the tcf_exts_destroy(), should we call it after the RCU updating, after `rcu_assign_pointer(tp->root, cp)` ? Or the concurrent RCU readers may derefer this freed memory (Please correct me If I am wrong).
On Sun, Nov 06, 2022 at 10:55:31PM +0800, Hawkins Jiawei wrote: > Hi Cong, > > > > > > > diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c > > index 1c9eeb98d826..00a6c04a4b42 100644 > > --- a/net/sched/cls_tcindex.c > > +++ b/net/sched/cls_tcindex.c > > @@ -479,6 +479,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > > } > > > > if (old_r && old_r != r) { > > + tcf_exts_destroy(&old_r->exts); > > err = tcindex_filter_result_init(old_r, cp, net); > > if (err < 0) { > > kfree(f); > > As for the position of the tcf_exts_destroy(), should we > call it after the RCU updating, after > `rcu_assign_pointer(tp->root, cp)` ? > > Or the concurrent RCU readers may derefer this freed memory > (Please correct me If I am wrong). I don't think so, because we already have tcf_exts_change() in multiple places within tcindex_set_parms(). Even if this is really a problem, moving it after rcu_assign_pointer() does not help, you need to wait for a grace period. Thanks.
On Mon, 7 Nov 2022 at 01:49, Cong Wang <xiyou.wangcong@gmail.com> wrote: > > On Sun, Nov 06, 2022 at 10:55:31PM +0800, Hawkins Jiawei wrote: > > Hi Cong, > > > > > > > > > > > diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c > > > index 1c9eeb98d826..00a6c04a4b42 100644 > > > --- a/net/sched/cls_tcindex.c > > > +++ b/net/sched/cls_tcindex.c > > > @@ -479,6 +479,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > > > } > > > > > > if (old_r && old_r != r) { > > > + tcf_exts_destroy(&old_r->exts); > > > err = tcindex_filter_result_init(old_r, cp, net); > > > if (err < 0) { > > > kfree(f); > > > > As for the position of the tcf_exts_destroy(), should we > > call it after the RCU updating, after > > `rcu_assign_pointer(tp->root, cp)` ? > > > > Or the concurrent RCU readers may derefer this freed memory > > (Please correct me If I am wrong). > > I don't think so, because we already have tcf_exts_change() in multiple > places within tcindex_set_parms(). Even if this is really a problem, Do you mean that, if this is a problem, then these tcf_exts_change() should have already triggered the Use-after-Free?(Please correct me if I get wrong) But it seems that these tcf_exts_change() don't destory the old_r, so it doesn't face the above concurrent problems. I find there are two tcf_exts_chang() in tcindex_set_parms(). One is oldp = p; r->res = cr; tcf_exts_change(&r->exts, &e); rcu_assign_pointer(tp->root, cp); the other is f->result.res = r->res; tcf_exts_change(&f->result.exts, &r->exts); fp = cp->h + (handle % cp->hash); for (nfp = rtnl_dereference(*fp); nfp; fp = &nfp->next, nfp = rtnl_dereference(*fp)) ; /* nothing */ rcu_assign_pointer(*fp, f); *r->exts* or *f->result.exts*, both are newly allocated in `tcindex_set_params()`, so the concurrent RCU readers won't read them before RCU updating. > moving it after rcu_assign_pointer() does not help, you need to wait for > a grace period. Yes, you are right. So if this is really a problem, I wonder if we can add the synchronize_rcu() before freeing the old->exts, like: diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c index 1c9eeb98d826..57d900c664cf 100644 --- a/net/sched/cls_tcindex.c +++ b/net/sched/cls_tcindex.c @@ -338,6 +338,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, struct tcf_result cr = {}; int err, balloc = 0; struct tcf_exts e; + struct tcf_exts old_e = {}; err = tcf_exts_init(&e, net, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE); if (err < 0) @@ -479,6 +480,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, } if (old_r && old_r != r) { + old_e = old_r->exts; err = tcindex_filter_result_init(old_r, cp, net); if (err < 0) { kfree(f); @@ -510,6 +512,9 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, tcf_exts_destroy(&new_filter_result.exts); } + synchronize_rcu(); + tcf_exts_destroy(&old_e); + if (oldp) tcf_queue_work(&oldp->rwork, tcindex_partial_destroy_work); return 0; > > Thanks.
diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c index 1c9eeb98d826..dc872a794337 100644 --- a/net/sched/cls_tcindex.c +++ b/net/sched/cls_tcindex.c @@ -338,6 +338,9 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, struct tcf_result cr = {}; int err, balloc = 0; struct tcf_exts e; +#ifdef CONFIG_NET_CLS_ACT + struct tcf_exts old_e = {}; +#endif err = tcf_exts_init(&e, net, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE); if (err < 0) @@ -479,6 +482,14 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, } if (old_r && old_r != r) { +#ifdef CONFIG_NET_CLS_ACT + /* r->exts is not copied from old_r->exts, and + * the following code will clears the old_r, so + * we need to destroy it after updating the tp->root, + * to avoid memory leak bug. + */ + old_e = old_r->exts; +#endif err = tcindex_filter_result_init(old_r, cp, net); if (err < 0) { kfree(f); @@ -510,6 +521,9 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, tcf_exts_destroy(&new_filter_result.exts); } +#ifdef CONFIG_NET_CLS_ACT + tcf_exts_destroy(&old_e); +#endif if (oldp) tcf_queue_work(&oldp->rwork, tcindex_partial_destroy_work); return 0;
Syzkaller reports a memory leak as follows: ==================================== BUG: memory leak unreferenced object 0xffff88810c287f00 (size 256): comm "syz-executor105", pid 3600, jiffies 4294943292 (age 12.990s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<ffffffff814cf9f0>] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046 [<ffffffff839c9e07>] kmalloc include/linux/slab.h:576 [inline] [<ffffffff839c9e07>] kmalloc_array include/linux/slab.h:627 [inline] [<ffffffff839c9e07>] kcalloc include/linux/slab.h:659 [inline] [<ffffffff839c9e07>] tcf_exts_init include/net/pkt_cls.h:250 [inline] [<ffffffff839c9e07>] tcindex_set_parms+0xa7/0xbe0 net/sched/cls_tcindex.c:342 [<ffffffff839caa1f>] tcindex_change+0xdf/0x120 net/sched/cls_tcindex.c:553 [<ffffffff8394db62>] tc_new_tfilter+0x4f2/0x1100 net/sched/cls_api.c:2147 [<ffffffff8389e91c>] rtnetlink_rcv_msg+0x4dc/0x5d0 net/core/rtnetlink.c:6082 [<ffffffff839eba67>] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2540 [<ffffffff839eab87>] netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] [<ffffffff839eab87>] netlink_unicast+0x397/0x4c0 net/netlink/af_netlink.c:1345 [<ffffffff839eb046>] netlink_sendmsg+0x396/0x710 net/netlink/af_netlink.c:1921 [<ffffffff8383e796>] sock_sendmsg_nosec net/socket.c:714 [inline] [<ffffffff8383e796>] sock_sendmsg+0x56/0x80 net/socket.c:734 [<ffffffff8383eb08>] ____sys_sendmsg+0x178/0x410 net/socket.c:2482 [<ffffffff83843678>] ___sys_sendmsg+0xa8/0x110 net/socket.c:2536 [<ffffffff838439c5>] __sys_sendmmsg+0x105/0x330 net/socket.c:2622 [<ffffffff83843c14>] __do_sys_sendmmsg net/socket.c:2651 [inline] [<ffffffff83843c14>] __se_sys_sendmmsg net/socket.c:2648 [inline] [<ffffffff83843c14>] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2648 [<ffffffff84605fd5>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<ffffffff84605fd5>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 [<ffffffff84800087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd ==================================== Kernel will uses tcindex_change() to change an existing traffic-control-indices filter properties. During the process of changing, kernel will clears the old traffic-control-indices filter result, and updates it by RCU assigning new traffic-control-indices data. Yet the problem is that, kernel will clears the old traffic-control-indices filter result, without destroying its tcf_exts structure, which triggers the above memory leak. This patch solves it by using tcf_exts_destroy() to destroy the tcf_exts structure in old traffic-control-indices filter result. Link: https://lore.kernel.org/all/0000000000001de5c505ebc9ec59@google.com/ Reported-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com Tested-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com Signed-off-by: Hawkins Jiawei <yin31149@gmail.com> --- net/sched/cls_tcindex.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)