From: Eric Dumazet edumazet@google.com
[ Upstream commit db3fa271022dacb9f741b96ea4714461a8911bb9 ]
__in6_dev_get(dev) called from inet6_set_link_af() can return NULL.
The needed check has been recently removed, let's add it back.
While do_setlink() does call validate_linkmsg() : ... err = validate_linkmsg(dev, tb); /* OK at this point */ ...
It is possible that the following call happening before the ->set_link_af() removes IPv6 if MTU is less than 1280 :
if (tb[IFLA_MTU]) { err = dev_set_mtu_ext(dev, nla_get_u32(tb[IFLA_MTU]), extack); if (err < 0) goto errout; status |= DO_SETLINK_MODIFIED; } ...
if (tb[IFLA_AF_SPEC]) { ... err = af_ops->set_link_af(dev, af); ->inet6_set_link_af() // CRASH because idev is NULL
Please note that IPv4 is immune to the bug since inet_set_link_af() does :
struct in_device *in_dev = __in_dev_get_rcu(dev); if (!in_dev) return -EAFNOSUPPORT;
This problem has been mentioned in commit cf7afbfeb8ce ("rtnl: make link af-specific updates atomic") changelog :
This method is not fail proof, while it is currently sufficient to make set_link_af() inerrable and thus 100% atomic, the validation function method will not be able to detect all error scenarios in the future, there will likely always be errors depending on states which are f.e. not protected by rtnl_mutex and thus may change between validation and setting.
IPv6: ADDRCONF(NETDEV_CHANGE): lo: link becomes ready general protection fault, probably for non-canonical address 0xdffffc0000000056: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x00000000000002b0-0x00000000000002b7] CPU: 0 PID: 9698 Comm: syz-executor712 Not tainted 5.5.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:inet6_set_link_af+0x66e/0xae0 net/ipv6/addrconf.c:5733 Code: 38 d0 7f 08 84 c0 0f 85 20 03 00 00 48 8d bb b0 02 00 00 45 0f b6 64 24 04 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 1a 03 00 00 44 89 a3 b0 02 00 RSP: 0018:ffffc90005b06d40 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff86df39a6 RDX: 0000000000000056 RSI: ffffffff86df3e74 RDI: 00000000000002b0 RBP: ffffc90005b06e70 R08: ffff8880a2ac0380 R09: ffffc90005b06db0 R10: fffff52000b60dbe R11: ffffc90005b06df7 R12: 0000000000000000 R13: 0000000000000000 R14: ffff8880a1fcc424 R15: dffffc0000000000 FS: 0000000000c46880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055f0494ca0d0 CR3: 000000009e4ac000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: do_setlink+0x2a9f/0x3720 net/core/rtnetlink.c:2754 rtnl_group_changelink net/core/rtnetlink.c:3103 [inline] __rtnl_newlink+0xdd1/0x1790 net/core/rtnetlink.c:3257 rtnl_newlink+0x69/0xa0 net/core/rtnetlink.c:3377 rtnetlink_rcv_msg+0x45e/0xaf0 net/core/rtnetlink.c:5438 netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477 rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5456 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline] netlink_unicast+0x59e/0x7e0 net/netlink/af_netlink.c:1328 netlink_sendmsg+0x91c/0xea0 net/netlink/af_netlink.c:1917 sock_sendmsg_nosec net/socket.c:652 [inline] sock_sendmsg+0xd7/0x130 net/socket.c:672 ____sys_sendmsg+0x753/0x880 net/socket.c:2343 ___sys_sendmsg+0x100/0x170 net/socket.c:2397 __sys_sendmsg+0x105/0x1d0 net/socket.c:2430 __do_sys_sendmsg net/socket.c:2439 [inline] __se_sys_sendmsg net/socket.c:2437 [inline] __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2437 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4402e9 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fffd62fbcf8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004402e9 RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000003 RBP: 00000000006ca018 R08: 0000000000000008 R09: 00000000004002c8 R10: 0000000000000005 R11: 0000000000000246 R12: 0000000000401b70 R13: 0000000000401c00 R14: 0000000000000000 R15: 0000000000000000 Modules linked in: ---[ end trace cfa7664b8fdcdff3 ]--- RIP: 0010:inet6_set_link_af+0x66e/0xae0 net/ipv6/addrconf.c:5733 Code: 38 d0 7f 08 84 c0 0f 85 20 03 00 00 48 8d bb b0 02 00 00 45 0f b6 64 24 04 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 1a 03 00 00 44 89 a3 b0 02 00 RSP: 0018:ffffc90005b06d40 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff86df39a6 RDX: 0000000000000056 RSI: ffffffff86df3e74 RDI: 00000000000002b0 RBP: ffffc90005b06e70 R08: ffff8880a2ac0380 R09: ffffc90005b06db0 R10: fffff52000b60dbe R11: ffffc90005b06df7 R12: 0000000000000000 R13: 0000000000000000 R14: ffff8880a1fcc424 R15: dffffc0000000000 FS: 0000000000c46880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000004 CR3: 000000009e4ac000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Fixes: 7dc2bccab0ee ("Validate required parameters in inet6_validate_link_af") Signed-off-by: Eric Dumazet edumazet@google.com Bisected-and-reported-by: syzbot syzkaller@googlegroups.com Cc: Maxim Mikityanskiy maximmi@mellanox.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv6/addrconf.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -5719,6 +5719,9 @@ static int inet6_set_link_af(struct net_ struct nlattr *tb[IFLA_INET6_MAX + 1]; int err;
+ if (!idev) + return -EAFNOSUPPORT; + if (nla_parse_nested_deprecated(tb, IFLA_INET6_MAX, nla, NULL, NULL) < 0) BUG();