Messages in this thread | | | From | Dmitry Vyukov <> | Date | Tue, 15 Nov 2022 12:39:56 +0100 | Subject | Re: [PATCH v2] net: sched: fix memory leak in tcindex_set_parms |
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On Tue, 15 Nov 2022 at 12:36, Paolo Abeni <pabeni@redhat.com> wrote: > > On Mon, 2022-11-14 at 01:05 +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 uses tcindex_change() to change an existing > > traffic-control-indices filter properties. During the > > process of changing, kernel 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 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, after the > > RCU grace period. > > > > [Thanks to the suggestion from Jakub Kicinski and Cong Wang] > > > > Fixes: b9a24bb76bf6 ("net_sched: properly handle failure case of tcf_exts_init()") > > Link: https://lore.kernel.org/all/0000000000001de5c505ebc9ec59@google.com/ > > Reported-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com > > Tested-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com > > Cc: Cong Wang <cong.wang@bytedance.com> > > Cc: Jakub Kicinski <kuba@kernel.org> > > Signed-off-by: Hawkins Jiawei <yin31149@gmail.com> > > --- > > v2: > > - remove all 'will' in commit message according to Jakub Kicinski > > - add Fixes tag according to Jakub Kicinski > > - remove all ifdefs according to Jakub Kicinski and Cong Wang > > - add synchronize_rcu() before destorying old_e according to > > Cong Wang > > > > v1: https://lore.kernel.org/all/20221031060835.11722-1-yin31149@gmail.com/ > > net/sched/cls_tcindex.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c > > index 1c9eeb98d826..d2fac9559d3e 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 +512,12 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > > tcf_exts_destroy(&new_filter_result.exts); > > } > > > > + /* Note: old_e should be destroyed after the RCU grace period, > > + * to avoid possible use-after-free by concurrent readers. > > + */ > > + synchronize_rcu(); > > this could make tc reconfiguration potentially very slow. I'm wondering > if we can delegate the tcf_exts_destroy() to some workqueue?
call_rcu?
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