kernel/linux.git/include/net/ip.h, branch linux-5.8.y

net/ipv4: always honour route mtu during forwarding

2020-10-29T09:07:02+00:00

[ Upstream commit 02a1b175b0e92d9e0fa5df3957ade8d733ceb6a0 ] Documentation/networking/ip-sysctl.txt:46 says: ip_forward_use_pmtu - BOOLEAN By default we don't trust protocol path MTUs while forwarding because they could be easily forged and can lead to unwanted fragmentation by the router. You only need to enable this if you have user-space software which tries to discover path mtus by itself and depends on the kernel honoring this information. This is normally not the case. Default: 0 (disabled) Possible values: 0 - disabled 1 - enabled Which makes it pretty clear that setting it to 1 is a potential security/safety/DoS issue, and yet it is entirely reasonable to want forwarded traffic to honour explicitly administrator configured route mtus (instead of defaulting to device mtu). Indeed, I can't think of a single reason why you wouldn't want to. Since you configured a route mtu you probably know better... It is pretty common to have a higher device mtu to allow receiving large (jumbo) frames, while having some routes via that interface (potentially including the default route to the internet) specify a lower mtu. Note that ipv6 forwarding uses device mtu unless the route is locked (in which case it will use the route mtu). This approach is not usable for IPv4 where an 'mtu lock' on a route also has the side effect of disabling TCP path mtu discovery via disabling the IPv4 DF (don't frag) bit on all outgoing frames. I'm not aware of a way to lock a route from an IPv6 RA, so that also potentially seems wrong. Signed-off-by: Maciej Żenczykowski Cc: Eric Dumazet Cc: Willem de Bruijn Cc: Lorenzo Colitti Cc: Sunmeet Gill (Sunny) Cc: Vinay Paradkar Cc: Tyler Wear Cc: David Ahern Reviewed-by: Eric Dumazet Signed-off-by: Greg Kroah-Hartman

ipv4: add ip_sock_set_pktinfo

2020-05-28T18:11:45+00:00

Add a helper to directly set the IP_PKTINFO sockopt from kernel space without going through a fake uaccess. Signed-off-by: Christoph Hellwig Signed-off-by: David S. Miller

ipv4: add ip_sock_set_mtu_discover

2020-05-28T18:11:45+00:00

Add a helper to directly set the IP_MTU_DISCOVER sockopt from kernel space without going through a fake uaccess. Signed-off-by: Christoph Hellwig Reviewed-by: David Howells [rxrpc bits] Signed-off-by: David S. Miller

ipv4: add ip_sock_set_recverr

2020-05-28T18:11:45+00:00

Add a helper to directly set the IP_RECVERR sockopt from kernel space without going through a fake uaccess. Signed-off-by: Christoph Hellwig Reviewed-by: David Howells Signed-off-by: David S. Miller

ipv4: add ip_sock_set_freebind

2020-05-28T18:11:45+00:00

Add a helper to directly set the IP_FREEBIND sockopt from kernel space without going through a fake uaccess. Signed-off-by: Christoph Hellwig Signed-off-by: David S. Miller

ipv4: add ip_sock_set_tos

2020-05-28T18:11:45+00:00

Add a helper to directly set the IP_TOS sockopt from kernel space without going through a fake uaccess. Signed-off-by: Christoph Hellwig Acked-by: Sagi Grimberg Signed-off-by: David S. Miller

inet: protect against too small mtu values.

2019-12-07T19:55:11+00:00

syzbot was once again able to crash a host by setting a very small mtu on loopback device. Let's make inetdev_valid_mtu() available in include/net/ip.h, and use it in ip_setup_cork(), so that we protect both ip_append_page() and __ip_append_data() Also add a READ_ONCE() when the device mtu is read. Pairs this lockless read with one WRITE_ONCE() in __dev_set_mtu(), even if other code paths might write over this field. Add a big comment in include/linux/netdevice.h about dev->mtu needing READ_ONCE()/WRITE_ONCE() annotations. Hopefully we will add the missing ones in followup patches. [1] refcount_t: saturated; leaking memory. WARNING: CPU: 0 PID: 9464 at lib/refcount.c:22 refcount_warn_saturate+0x138/0x1f0 lib/refcount.c:22 Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 9464 Comm: syz-executor850 Not tainted 5.4.0-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+0x138/0x1f0 lib/refcount.c:22 Code: 06 31 ff 89 de e8 c8 f5 e6 fd 84 db 0f 85 6f ff ff ff e8 7b f4 e6 fd 48 c7 c7 e0 71 4f 88 c6 05 56 a6 a4 06 01 e8 c7 a8 b7 fd <0f> 0b e9 50 ff ff ff e8 5c f4 e6 fd 0f b6 1d 3d a6 a4 06 31 ff 89 RSP: 0018:ffff88809689f550 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff815e4336 RDI: ffffed1012d13e9c RBP: ffff88809689f560 R08: ffff88809c50a3c0 R09: fffffbfff15d31b1 R10: fffffbfff15d31b0 R11: ffffffff8ae98d87 R12: 0000000000000001 R13: 0000000000040100 R14: ffff888099041104 R15: ffff888218d96e40 refcount_add include/linux/refcount.h:193 [inline] skb_set_owner_w+0x2b6/0x410 net/core/sock.c:1999 sock_wmalloc+0xf1/0x120 net/core/sock.c:2096 ip_append_page+0x7ef/0x1190 net/ipv4/ip_output.c:1383 udp_sendpage+0x1c7/0x480 net/ipv4/udp.c:1276 inet_sendpage+0xdb/0x150 net/ipv4/af_inet.c:821 kernel_sendpage+0x92/0xf0 net/socket.c:3794 sock_sendpage+0x8b/0xc0 net/socket.c:936 pipe_to_sendpage+0x2da/0x3c0 fs/splice.c:458 splice_from_pipe_feed fs/splice.c:512 [inline] __splice_from_pipe+0x3ee/0x7c0 fs/splice.c:636 splice_from_pipe+0x108/0x170 fs/splice.c:671 generic_splice_sendpage+0x3c/0x50 fs/splice.c:842 do_splice_from fs/splice.c:861 [inline] direct_splice_actor+0x123/0x190 fs/splice.c:1035 splice_direct_to_actor+0x3b4/0xa30 fs/splice.c:990 do_splice_direct+0x1da/0x2a0 fs/splice.c:1078 do_sendfile+0x597/0xd00 fs/read_write.c:1464 __do_sys_sendfile64 fs/read_write.c:1525 [inline] __se_sys_sendfile64 fs/read_write.c:1511 [inline] __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1511 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x441409 Code: e8 ac e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 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 eb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fffb64c4f78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441409 RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000005 RBP: 0000000000073b8a R08: 0000000000000010 R09: 0000000000000010 R10: 0000000000010001 R11: 0000000000000246 R12: 0000000000402180 R13: 0000000000402210 R14: 0000000000000000 R15: 0000000000000000 Kernel Offset: disabled Rebooting in 86400 seconds.. Fixes: 1470ddf7f8ce ("inet: Remove explicit write references to sk/inet in ip_append_data") Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller

net: inet_is_local_reserved_port() port arg should be unsigned short

2019-11-26T23:15:07+00:00

Any argument outside of that range would result in an out of bound memory access, since the accessed array is 65536 bits long. Signed-off-by: Maciej Żenczykowski Signed-off-by: David S. Miller

net: port < inet_prot_sock(net) --> inet_port_requires_bind_service(net, port)

2019-11-26T21:20:46+00:00

Note that the sysctl write accessor functions guarantee that: net->ipv4.sysctl_ip_prot_sock <= net->ipv4.ip_local_ports.range[0] invariant is maintained, and as such the max() in selinux hooks is actually spurious. ie. even though if (snum < max(inet_prot_sock(sock_net(sk)), low) || snum > high) { per logic is the same as if ((snum < inet_prot_sock(sock_net(sk)) && snum < low) || snum > high) { it is actually functionally equivalent to: if (snum < low || snum > high) { which is equivalent to: if (snum < inet_prot_sock(sock_net(sk)) || snum < low || snum > high) { even though the first clause is spurious. But we want to hold on to it in case we ever want to change what what inet_port_requires_bind_service() means (for example by changing it from a, by default, [0..1024) range to some sort of set). Test: builds, git 'grep inet_prot_sock' finds no other references Cc: Eric Dumazet Signed-off-by: Maciej Żenczykowski Signed-off-by: David S. Miller

net: inet_is_local_reserved_port() should return bool not int

2019-11-23T00:52:47+00:00

Cc: Eric Dumazet Signed-off-by: Maciej Żenczykowski Signed-off-by: Jakub Kicinski