Messages in this thread Patch in this message | | | From | Hawkins Jiawei <> | Subject | [PATCH v2] net: sched: fix memory leak in tcindex_set_parms | Date | Mon, 14 Nov 2022 01:05:08 +0800 |
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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(); + tcf_exts_destroy(&old_e); + if (oldp) tcf_queue_work(&oldp->rwork, tcindex_partial_destroy_work); return 0; -- 2.25.1
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