On 3/1/20 6:22 PM, Eric Dumazet wrote: > > > On 3/1/20 5:33 PM, syzbot wrote: >> Hello, >> >> syzbot found the following crash on: >> >> HEAD commit: fd786fb1 net: convert suitable drivers to use phy_do_ioctl.. >> git tree: net-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=14e9726ee00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=7f93900a7904130d >> dashboard link: https://syzkaller.appspot.com/bug?extid=dd803bc0e8adf0003261 >> compiler: gcc (GCC) 9.0.0 20181231 (experimental) >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12af9369e00000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10583d76e00000 >> >> The bug was bisected to: >> >> commit 14215108a1fd7e002c0a1f9faf8fbaf41fdda50d >> Author: Cong Wang <xiyou.wangcong@xxxxxxxxx> >> Date: Thu Feb 21 05:37:42 2019 +0000 >> >> net_sched: initialize net pointer inside tcf_exts_init() >> >> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=175b66bee00000 >> final crash: https://syzkaller.appspot.com/x/report.txt?x=14db66bee00000 >> console output: https://syzkaller.appspot.com/x/log.txt?x=10db66bee00000 >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+dd803bc0e8adf0003261@xxxxxxxxxxxxxxxxxxxxxxxxx >> Fixes: 14215108a1fd ("net_sched: initialize net pointer inside tcf_exts_init()") >> >> RBP: 0000000000000000 R08: 0000000000000002 R09: 00000000bb1414ac >> R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff >> R13: 0000000000000009 R14: 0000000000000000 R15: 0000000000000000 >> ------------[ cut here ]------------ >> refcount_t: underflow; use-after-free. >> WARNING: CPU: 1 PID: 9577 at lib/refcount.c:28 refcount_warn_saturate+0x1dc/0x1f0 lib/refcount.c:28 >> Kernel panic - not syncing: panic_on_warn set ... >> CPU: 1 PID: 9577 Comm: syz-executor327 Not tainted 5.5.0-rc6-syzkaller #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> Call Trace: >> __dump_stack lib/dump_stack.c:77 [inline] >> dump_stack+0x197/0x210 lib/dump_stack.c:118 >> panic+0x2e3/0x75c kernel/panic.c:221 >> __warn.cold+0x2f/0x3e kernel/panic.c:582 >> report_bug+0x289/0x300 lib/bug.c:195 >> fixup_bug arch/x86/kernel/traps.c:174 [inline] >> fixup_bug arch/x86/kernel/traps.c:169 [inline] >> do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267 >> do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286 >> invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027 >> RIP: 0010:refcount_warn_saturate+0x1dc/0x1f0 lib/refcount.c:28 >> Code: e9 d8 fe ff ff 48 89 df e8 c1 f8 16 fe e9 85 fe ff ff e8 a7 77 d8 fd 48 c7 c7 e0 44 71 88 c6 05 9e 86 db 06 01 e8 93 27 a9 fd <0f> 0b e9 ac fe ff ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 55 48 >> RSP: 0018:ffffc9000c067b00 EFLAGS: 00010282 >> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 >> RDX: 0000000000000000 RSI: ffffffff815e5dd6 RDI: fffff5200180cf52 >> RBP: ffffc9000c067b10 R08: ffff8880a8630340 R09: ffffed1015d26621 >> R10: ffffed1015d26620 R11: ffff8880ae933107 R12: 0000000000000003 >> R13: ffff888090256000 R14: ffff8880a7e5c040 R15: ffff8880a7e5c044 >> refcount_sub_and_test include/linux/refcount.h:261 [inline] >> refcount_dec_and_test include/linux/refcount.h:281 [inline] >> put_net include/net/net_namespace.h:259 [inline] >> __sk_destruct+0x6d8/0x7f0 net/core/sock.c:1723 >> sk_destruct+0xd5/0x110 net/core/sock.c:1739 >> __sk_free+0xfb/0x3f0 net/core/sock.c:1750 >> sk_free+0x83/0xb0 net/core/sock.c:1761 >> sock_put include/net/sock.h:1719 [inline] >> __tun_detach+0xbe0/0x1150 drivers/net/tun.c:728 >> tun_detach drivers/net/tun.c:740 [inline] >> tun_chr_close+0xe0/0x180 drivers/net/tun.c:3455 >> __fput+0x2ff/0x890 fs/file_table.c:280 >> ____fput+0x16/0x20 fs/file_table.c:313 >> task_work_run+0x145/0x1c0 kernel/task_work.c:113 >> exit_task_work include/linux/task_work.h:22 [inline] >> do_exit+0xba9/0x2f50 kernel/exit.c:801 >> do_group_exit+0x135/0x360 kernel/exit.c:899 >> __do_sys_exit_group kernel/exit.c:910 [inline] >> __se_sys_exit_group kernel/exit.c:908 [inline] >> __x64_sys_exit_group+0x44/0x50 kernel/exit.c:908 >> do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> RIP: 0033:0x441a48 >> Code: Bad RIP value. >> RSP: 002b:00007fffe55809a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 >> RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000441a48 >> RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001 >> RBP: 00000000004c8430 R08: 00000000000000e7 R09: ffffffffffffffd0 >> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 >> R13: 00000000006dba80 R14: 0000000000000000 R15: 0000000000000000 >> Kernel Offset: disabled >> Rebooting in 86400 seconds.. >> >> >> --- >> This bug is generated by a bot. It may contain errors. >> See https://goo.gl/tpsmEJ for more information about syzbot. >> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. >> >> syzbot will keep track of this bug report. See: >> https://goo.gl/tpsmEJ#status for how to communicate with syzbot. >> For information about bisection process see: https://goo.gl/tpsmEJ#bisection >> syzbot can test patches for this bug, for details see: >> https://goo.gl/tpsmEJ#testing-patches >> > > > Hmmm... maybe this patch would fix it ? > > diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h > index a972244ab1931a2fd52a41efa4f7a6cd78d8746a..6e258a6c1328e38a757d9711f4116a6672995b8f 100644 > --- a/include/net/pkt_cls.h > +++ b/include/net/pkt_cls.h > @@ -206,11 +206,12 @@ static inline int tcf_exts_init(struct tcf_exts *exts, struct net *net, > #ifdef CONFIG_NET_CLS_ACT > exts->type = 0; > exts->nr_actions = 0; > - exts->net = net; > + exts->net = NULL; > exts->actions = kcalloc(TCA_ACT_MAX_PRIO, sizeof(struct tc_action *), > GFP_KERNEL); > if (!exts->actions) > return -ENOMEM; > + exts->net = net; > #endif > exts->action = action; > exts->police = police; > Hmm no. Instead, make sure cls_u32 gets a reference so that calls to u32_destroy_key(new, false); do not end up decrementing netns refcount. diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index e15ff335953deef36e55901d8f4ce34e15ed676f..587d71def49157680cf54f84558c4f4e5dad37f1 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -898,6 +898,7 @@ static int u32_change(struct net *net, struct sk_buff *in_skb, new = u32_init_knode(net, tp, n); if (!new) return -ENOMEM; + tcf_exts_get_net(&new->exts); err = u32_set_parms(net, tp, base, new, tb, tca[TCA_RATE], ovr, extack); @@ -918,7 +919,6 @@ static int u32_change(struct net *net, struct sk_buff *in_skb, u32_replace_knode(tp, tp_c, new); tcf_unbind_filter(tp, &n->res); - tcf_exts_get_net(&n->exts); tcf_queue_work(&n->rwork, u32_delete_key_work); return 0; }
