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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: 18801353760@163.com, syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com, Cong Wang , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] net: sched: fix memory leak in tcindex_set_parms Date: Mon, 14 Nov 2022 01:05:08 +0800 Message-Id: <20221113170507.8205-1-yin31149@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Spam-Status: No, score=-1.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1749402205149978177?= X-GMAIL-MSGID: =?utf-8?q?1749402205149978177?= 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: [] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046 [] kmalloc include/linux/slab.h:576 [inline] [] kmalloc_array include/linux/slab.h:627 [inline] [] kcalloc include/linux/slab.h:659 [inline] [] tcf_exts_init include/net/pkt_cls.h:250 [inline] [] tcindex_set_parms+0xa7/0xbe0 net/sched/cls_tcindex.c:342 [] tcindex_change+0xdf/0x120 net/sched/cls_tcindex.c:553 [] tc_new_tfilter+0x4f2/0x1100 net/sched/cls_api.c:2147 [] rtnetlink_rcv_msg+0x4dc/0x5d0 net/core/rtnetlink.c:6082 [] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2540 [] netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] [] netlink_unicast+0x397/0x4c0 net/netlink/af_netlink.c:1345 [] netlink_sendmsg+0x396/0x710 net/netlink/af_netlink.c:1921 [] sock_sendmsg_nosec net/socket.c:714 [inline] [] sock_sendmsg+0x56/0x80 net/socket.c:734 [] ____sys_sendmsg+0x178/0x410 net/socket.c:2482 [] ___sys_sendmsg+0xa8/0x110 net/socket.c:2536 [] __sys_sendmmsg+0x105/0x330 net/socket.c:2622 [] __do_sys_sendmmsg net/socket.c:2651 [inline] [] __se_sys_sendmmsg net/socket.c:2648 [inline] [] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2648 [] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 [] 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 Cc: Jakub Kicinski Signed-off-by: Hawkins Jiawei --- 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;