From: Eric Dumazet edumazet@google.com

commit 3db09e762dc79584a69c10d74a6b98f89a9979f8 upstream.

We are now able to detect extra put_net() at the moment they happen, instead of much later in correct code paths.

u32_init_knode() / tcf_exts_init() populates the ->exts.net pointer, but as mentioned in tcf_exts_init(), the refcount on netns has not been elevated yet.

The refcount is taken only once tcf_exts_get_net() is called.

So the two u32_destroy_key() calls from u32_change() are attempting to release an invalid reference on the netns.

syzbot report:

refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 0 PID: 21708 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0 lib/refcount.c:31 Modules linked in: CPU: 0 PID: 21708 Comm: syz-executor.5 Not tainted 5.18.0-rc2-next-20220412-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:refcount_warn_saturate+0xbf/0x1e0 lib/refcount.c:31 Code: 1d 14 b6 b2 09 31 ff 89 de e8 6d e9 89 fd 84 db 75 e0 e8 84 e5 89 fd 48 c7 c7 40 aa 26 8a c6 05 f4 b5 b2 09 01 e8 e5 81 2e 05 <0f> 0b eb c4 e8 68 e5 89 fd 0f b6 1d e3 b5 b2 09 31 ff 89 de e8 38 RSP: 0018:ffffc900051af1b0 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000040000 RSI: ffffffff8160a0c8 RDI: fffff52000a35e28 RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff81604a9e R11: 0000000000000000 R12: 1ffff92000a35e3b R13: 00000000ffffffef R14: ffff8880211a0194 R15: ffff8880577d0a00 FS: 00007f25d183e700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f19c859c028 CR3: 0000000051009000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> __refcount_dec include/linux/refcount.h:344 [inline] refcount_dec include/linux/refcount.h:359 [inline] ref_tracker_free+0x535/0x6b0 lib/ref_tracker.c:118 netns_tracker_free include/net/net_namespace.h:327 [inline] put_net_track include/net/net_namespace.h:341 [inline] tcf_exts_put_net include/net/pkt_cls.h:255 [inline] u32_destroy_key.isra.0+0xa7/0x2b0 net/sched/cls_u32.c:394 u32_change+0xe01/0x3140 net/sched/cls_u32.c:909 tc_new_tfilter+0x98d/0x2200 net/sched/cls_api.c:2148 rtnetlink_rcv_msg+0x80d/0xb80 net/core/rtnetlink.c:6016 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2495 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x543/0x7f0 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x904/0xe00 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:705 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:725 ____sys_sendmsg+0x6e2/0x800 net/socket.c:2413 ___sys_sendmsg+0xf3/0x170 net/socket.c:2467 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2496 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+0x44/0xae RIP: 0033:0x7f25d0689049 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f25d183e168 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f25d079c030 RCX: 00007f25d0689049 RDX: 0000000000000000 RSI: 0000000020000340 RDI: 0000000000000005 RBP: 00007f25d06e308d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffd0b752e3f R14: 00007f25d183e300 R15: 0000000000022000 </TASK>

Fixes: 35c55fc156d8 ("cls_u32: use tcf_exts_get_net() before call_rcu()") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Cc: Cong Wang xiyou.wangcong@gmail.com Cc: Jiri Pirko jiri@resnulli.us Acked-by: Jamal Hadi Salim jhs@mojatatu.com Signed-off-by: Jakub Kicinski kuba@kernel.org [rkolchmeyer: Backported to 4.19: adjusted u32_destroy_key() signature] Signed-off-by: Robert Kolchmeyer rkolchmeyer@google.com --- u32_destroy_key() takes an additional argument (struct tcf_proto *tp) on 4.19, so I updated the patch to include this. But u32_destroy_key() doesn't actually use this argument, so the semantics of the patch aren't impacted by this change.

net/sched/cls_u32.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index fe246e03fcd9c..ad82c63094821 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -404,15 +404,20 @@ static int u32_init(struct tcf_proto *tp) return 0; }

-static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n, - bool free_pf) +static void __u32_destroy_key(struct tc_u_knode *n) { struct tc_u_hnode *ht = rtnl_dereference(n->ht_down);

tcf_exts_destroy(&n->exts); - tcf_exts_put_net(&n->exts); if (ht && --ht->refcnt == 0) kfree(ht); + kfree(n); +} + +static void u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n, + bool free_pf) +{ + tcf_exts_put_net(&n->exts); #ifdef CONFIG_CLS_U32_PERF if (free_pf) free_percpu(n->pf); @@ -421,8 +426,7 @@ static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n, if (free_pf) free_percpu(n->pcpu_success); #endif - kfree(n); - return 0; + __u32_destroy_key(n); }

/* u32_delete_key_rcu should be called when free'ing a copied @@ -965,13 +969,13 @@ static int u32_change(struct net *net, struct sk_buff *in_skb, tca[TCA_RATE], ovr, extack);

if (err) { - u32_destroy_key(tp, new, false); + __u32_destroy_key(new); return err; }

err = u32_replace_hw_knode(tp, new, flags, extack); if (err) { - u32_destroy_key(tp, new, false); + __u32_destroy_key(new); return err; }