From: Eric Dumazet edumazet@google.com
commit 7f700334be9aeb91d5d86ef9ad2d901b9b453e9b upstream.
After adopting CONFIG_PCPU_DEV_REFCNT=n option, syzbot was able to trigger a warning [1]
Issue here is that:
- all dev_put() should be paired with a corresponding dev_hold(), and vice versa.
- A driver doing a dev_put() in its ndo_uninit() MUST also do a dev_hold() in its ndo_init(), only when ndo_init() is returning 0.
Otherwise, register_netdevice() would call ndo_uninit() in its error path and release a refcount too soon.
ip6_gre for example (among others problematic drivers) has to use dev_hold() in ip6gre_tunnel_init_common() instead of from ip6gre_newlink_common(), covering both ip6gre_tunnel_init() and ip6gre_tap_init()/
Note that ip6gre_tunnel_init_common() is not called from ip6erspan_tap_init() thus we also need to add a dev_hold() there, as ip6erspan_tunnel_uninit() does call dev_put()
[1] refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 0 PID: 8422 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0 lib/refcount.c:31 Modules linked in: CPU: 1 PID: 8422 Comm: syz-executor854 Not tainted 5.12.0-rc4-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 6a 5a e8 09 31 ff 89 de e8 8d 1a ab fd 84 db 75 e0 e8 d4 13 ab fd 48 c7 c7 a0 e1 c1 89 c6 05 4a 5a e8 09 01 e8 2e 36 fb 04 <0f> 0b eb c4 e8 b8 13 ab fd 0f b6 1d 39 5a e8 09 31 ff 89 de e8 58 RSP: 0018:ffffc900018befd0 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff88801ef19c40 RSI: ffffffff815c51f5 RDI: fffff52000317dec RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffff815bdf8e R11: 0000000000000000 R12: ffff888018cf4568 R13: ffff888018cf4c00 R14: ffff8880228f2000 R15: ffffffff8d659b80 FS: 00000000014eb300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055d7bf2b3138 CR3: 0000000014933000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __refcount_dec include/linux/refcount.h:344 [inline] refcount_dec include/linux/refcount.h:359 [inline] dev_put include/linux/netdevice.h:4135 [inline] ip6gre_tunnel_uninit+0x3d7/0x440 net/ipv6/ip6_gre.c:420 register_netdevice+0xadf/0x1500 net/core/dev.c:10308 ip6gre_newlink_common.constprop.0+0x158/0x410 net/ipv6/ip6_gre.c:1984 ip6gre_newlink+0x275/0x7a0 net/ipv6/ip6_gre.c:2017 __rtnl_newlink+0x1062/0x1710 net/core/rtnetlink.c:3443 rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3491 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5553 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2502 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline] netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:674 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
Fixes: 919067cc845f ("net: add CONFIG_PCPU_DEV_REFCNT") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv6/ip6_gre.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -1496,6 +1496,7 @@ static int ip6gre_tunnel_init_common(str } ip6gre_tnl_init_features(dev);
+ dev_hold(dev); return 0;
cleanup_dst_cache_init: @@ -1889,6 +1890,7 @@ static int ip6erspan_tap_init(struct net dev->priv_flags |= IFF_LIVE_ADDR_CHANGE; ip6erspan_tnl_link_config(tunnel, 1);
+ dev_hold(dev); return 0;
cleanup_dst_cache_init: @@ -1988,8 +1990,6 @@ static int ip6gre_newlink_common(struct if (tb[IFLA_MTU]) ip6_tnl_change_mtu(dev, nla_get_u32(tb[IFLA_MTU]));
- dev_hold(dev); - out: return err; }