linux.git/net/ipv6/addrconf.c, branch v5.6-rc2

ipv6/addrconf: fix potential NULL deref in inet6_set_link_af()

2020-02-07T17:43:23+00:00

__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 
Bisected-and-reported-by: syzbot 
Cc: Maxim Mikityanskiy 
Signed-off-by: David S. Miller

ipv6/addrconf: only check invalid header values when NETLINK_F_STRICT_CHK is set

2019-12-14T01:13:49+00:00

In commit 4b1373de73a3 ("net: ipv6: addr: perform strict checks also for
doit handlers") we add strict check for inet6_rtm_getaddr(). But we did
the invalid header values check before checking if NETLINK_F_STRICT_CHK
is set. This may break backwards compatibility if user already set the
ifm->ifa_prefixlen, ifm->ifa_flags, ifm->ifa_scope in their netlink code.

I didn't move the nlmsg_len check because I thought it's a valid check.

Reported-by: Jianlin Shi 
Fixes: 4b1373de73a3 ("net: ipv6: addr: perform strict checks also for doit handlers")
Signed-off-by: Hangbin Liu 
Reviewed-by: David Ahern 
Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2019-10-05T20:37:23+00:00

ipv6: Handle missing host route in __ipv6_ifa_notify

2019-10-05T01:08:58+00:00

Rajendra reported a kernel panic when a link was taken down:

    [ 6870.263084] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8
    [ 6870.271856] IP: [] __ipv6_ifa_notify+0x154/0x290

    

    [ 6870.570501] Call Trace:
    [ 6870.573238] [] ? ipv6_ifa_notify+0x26/0x40
    [ 6870.579665] [] ? addrconf_dad_completed+0x4c/0x2c0
    [ 6870.586869] [] ? ipv6_dev_mc_inc+0x196/0x260
    [ 6870.593491] [] ? addrconf_dad_work+0x10a/0x430
    [ 6870.600305] [] ? __switch_to_asm+0x34/0x70
    [ 6870.606732] [] ? process_one_work+0x18a/0x430
    [ 6870.613449] [] ? worker_thread+0x4d/0x490
    [ 6870.619778] [] ? process_one_work+0x430/0x430
    [ 6870.626495] [] ? kthread+0xd9/0xf0
    [ 6870.632145] [] ? __switch_to_asm+0x34/0x70
    [ 6870.638573] [] ? kthread_park+0x60/0x60
    [ 6870.644707] [] ? ret_from_fork+0x57/0x70
    [ 6870.650936] Code: 31 c0 31 d2 41 b9 20 00 08 02 b9 09 00 00 0

addrconf_dad_work is kicked to be scheduled when a device is brought
up. There is a race between addrcond_dad_work getting scheduled and
taking the rtnl lock and a process taking the link down (under rtnl).
The latter removes the host route from the inet6_addr as part of
addrconf_ifdown which is run for NETDEV_DOWN. The former attempts
to use the host route in __ipv6_ifa_notify. If the down event removes
the host route due to the race to the rtnl, then the BUG listed above
occurs.

Since the DAD sequence can not be aborted, add a check for the missing
host route in __ipv6_ifa_notify. The only way this should happen is due
to the previously mentioned race. The host route is created when the
address is added to an interface; it is only removed on a down event
where the address is kept. Add a warning if the host route is missing
AND the device is up; this is a situation that should never happen.

Fixes: f1705ec197e7 ("net: ipv6: Make address flushing on ifdown optional")
Reported-by: Rajendra Dendukuri 
Signed-off-by: David Ahern 
Reviewed-by: Eric Dumazet 
Signed-off-by: David S. Miller

Revert "ipv6: Handle race in addrconf_dad_work"

2019-10-04T21:31:10+00:00

This reverts commit a3ce2a21bb8969ae27917281244fa91bf5f286d7.

Eric reported tests failings with commit. After digging into it,
the bottom line is that the DAD sequence is not to be messed with.
There are too many cases that are expected to proceed regardless
of whether a device is up.

Revert the patch and I will send a different solution for the
problem Rajendra reported.

Signed-off-by: David Ahern 
Cc: Eric Dumazet 
Reviewed-by: Eric Dumazet 
Signed-off-by: David S. Miller

ipv6: Handle race in addrconf_dad_work

2019-10-02T01:43:41+00:00

Rajendra reported a kernel panic when a link was taken down:

[ 6870.263084] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8
[ 6870.271856] IP: [] __ipv6_ifa_notify+0x154/0x290



[ 6870.570501] Call Trace:
[ 6870.573238] [] ? ipv6_ifa_notify+0x26/0x40
[ 6870.579665] [] ? addrconf_dad_completed+0x4c/0x2c0
[ 6870.586869] [] ? ipv6_dev_mc_inc+0x196/0x260
[ 6870.593491] [] ? addrconf_dad_work+0x10a/0x430
[ 6870.600305] [] ? __switch_to_asm+0x34/0x70
[ 6870.606732] [] ? process_one_work+0x18a/0x430
[ 6870.613449] [] ? worker_thread+0x4d/0x490
[ 6870.619778] [] ? process_one_work+0x430/0x430
[ 6870.626495] [] ? kthread+0xd9/0xf0
[ 6870.632145] [] ? __switch_to_asm+0x34/0x70
[ 6870.638573] [] ? kthread_park+0x60/0x60
[ 6870.644707] [] ? ret_from_fork+0x57/0x70
[ 6870.650936] Code: 31 c0 31 d2 41 b9 20 00 08 02 b9 09 00 00 0

addrconf_dad_work is kicked to be scheduled when a device is brought
up. There is a race between addrcond_dad_work getting scheduled and
taking the rtnl lock and a process taking the link down (under rtnl).
The latter removes the host route from the inet6_addr as part of
addrconf_ifdown which is run for NETDEV_DOWN. The former attempts
to use the host route in ipv6_ifa_notify. If the down event removes
the host route due to the race to the rtnl, then the BUG listed above
occurs.

This scenario does not occur when the ipv6 address is not kept
(net.ipv6.conf.all.keep_addr_on_down = 0) as addrconf_ifdown sets the
state of the ifp to DEAD. Handle when the addresses are kept by checking
IF_READY which is reset by addrconf_ifdown.

The 'dead' flag for an inet6_addr is set only under rtnl, in
addrconf_ifdown and it means the device is getting removed (or IPv6 is
disabled). The interesting cases for changing the idev flag are
addrconf_notify (NETDEV_UP and NETDEV_CHANGE) and addrconf_ifdown
(reset the flag). The former does not have the idev lock - only rtnl;
the latter has both. Based on that the existing dead + IF_READY check
can be moved to right after the rtnl_lock in addrconf_dad_work.

Fixes: f1705ec197e7 ("net: ipv6: Make address flushing on ifdown optional")
Reported-by: Rajendra Dendukuri 
Signed-off-by: David Ahern 
Reviewed-by: Eric Dumazet 
Signed-off-by: David S. Miller

ipv6: minor code reorg in inet6_fill_ifla6_attrs()

2019-10-01T21:59:03+00:00

Just put related code together to ease code reading: the memcpy() is
related to the nla_reserve().

Signed-off-by: Nicolas Dichtel 
Signed-off-by: David S. Miller

ipv6: propagate ipv6_add_dev's error returns out of ipv6_find_idev

2019-08-23T21:53:06+00:00

Currently, ipv6_find_idev returns NULL when ipv6_add_dev fails,
ignoring the specific error value. This results in addrconf_add_dev
returning ENOBUFS in all cases, which is unfortunate in cases such as:

    # ip link add dummyX type dummy
    # ip link set dummyX mtu 1200 up
    # ip addr add 2000::/64 dev dummyX
    RTNETLINK answers: No buffer space available

Commit a317a2f19da7 ("ipv6: fail early when creating netdev named all
or default") introduced error returns in ipv6_add_dev. Before that,
that function would simply return NULL for all failures.

Signed-off-by: Sabrina Dubroca 
Signed-off-by: David S. Miller

ipv6/addrconf: allow adding multicast addr if IFA_F_MCAUTOJOIN is set

2019-08-22T03:39:29+00:00

In commit 93a714d6b53d ("multicast: Extend ip address command to enable
multicast group join/leave on") we added a new flag IFA_F_MCAUTOJOIN
to make user able to add multicast address on ethernet interface.

This works for IPv4, but not for IPv6. See the inet6_addr_add code.

static int inet6_addr_add()
{
	...
	if (cfg->ifa_flags & IFA_F_MCAUTOJOIN) {
		ipv6_mc_config(net->ipv6.mc_autojoin_sk, true...)
	}

	ifp = ipv6_add_addr(idev, cfg, true, extack); <- always fail with maddr
	if (!IS_ERR(ifp)) {
		...
	} else if (cfg->ifa_flags & IFA_F_MCAUTOJOIN) {
		ipv6_mc_config(net->ipv6.mc_autojoin_sk, false...)
	}
}

But in ipv6_add_addr() it will check the address type and reject multicast
address directly. So this feature is never worked for IPv6.

We should not remove the multicast address check totally in ipv6_add_addr(),
but could accept multicast address only when IFA_F_MCAUTOJOIN flag supplied.

v2: update commit description

Fixes: 93a714d6b53d ("multicast: Extend ip address command to enable multicast group join/leave on")
Reported-by: Jianlin Shi 
Signed-off-by: Hangbin Liu 
Signed-off-by: David S. Miller

proc/sysctl: add shared variables for range check

2019-07-19T00:08:07+00:00

In the sysctl code the proc_dointvec_minmax() function is often used to
validate the user supplied value between an allowed range.  This
function uses the extra1 and extra2 members from struct ctl_table as
minimum and maximum allowed value.

On sysctl handler declaration, in every source file there are some
readonly variables containing just an integer which address is assigned
to the extra1 and extra2 members, so the sysctl range is enforced.

The special values 0, 1 and INT_MAX are very often used as range
boundary, leading duplication of variables like zero=0, one=1,
int_max=INT_MAX in different source files:

    $ git grep -E '\.extra[12].*&(zero|one|int_max)' |wc -l
    248

Add a const int array containing the most commonly used values, some
macros to refer more easily to the correct array member, and use them
instead of creating a local one for every object file.

This is the bloat-o-meter output comparing the old and new binary
compiled with the default Fedora config:

    # scripts/bloat-o-meter -d vmlinux.o.old vmlinux.o
    add/remove: 2/2 grow/shrink: 0/2 up/down: 24/-188 (-164)
    Data                                         old     new   delta
    sysctl_vals                                    -      12     +12
    __kstrtab_sysctl_vals                          -      12     +12
    max                                           14      10      -4
    int_max                                       16       -     -16
    one                                           68       -     -68
    zero                                         128      28    -100
    Total: Before=20583249, After=20583085, chg -0.00%

[mcroce@redhat.com: tipc: remove two unused variables]
  Link: http://lkml.kernel.org/r/20190530091952.4108-1-mcroce@redhat.com
[akpm@linux-foundation.org: fix net/ipv6/sysctl_net_ipv6.c]
[arnd@arndb.de: proc/sysctl: make firmware loader table conditional]
  Link: http://lkml.kernel.org/r/20190617130014.1713870-1-arnd@arndb.de
[akpm@linux-foundation.org: fix fs/eventpoll.c]
Link: http://lkml.kernel.org/r/20190430180111.10688-1-mcroce@redhat.com
Signed-off-by: Matteo Croce 
Signed-off-by: Arnd Bergmann 
Acked-by: Kees Cook 
Reviewed-by: Aaron Tomlin 
Cc: Matthew Wilcox 
Cc: Stephen Rothwell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds