linux-stable.git/net/ipv4, branch v3.2.64 Linux kernel stable tree ipv4: disable bh while doing route gc 2014-11-05T20:27:47+00:00 Marcelo Ricardo Leitner mleitner@redhat.com 2014-10-13T17:03:30+00:00 4715883ba814db9635baf74e378580bd27a534bd Further tests revealed that after moving the garbage collector to a work queue and protecting it with a spinlock may leave the system prone to soft lockups if bottom half gets very busy. It was reproced with a set of firewall rules that REJECTed packets. If the NIC bottom half handler ends up running on the same CPU that is running the garbage collector on a very large cache, the garbage collector will not be able to do its job due to the amount of work needed for handling the REJECTs and also won't reschedule. The fix is to disable bottom half during the garbage collecting, as it already was in the first place (most calls to it came from softirqs). Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
Further tests revealed that after moving the garbage collector to a work
queue and protecting it with a spinlock may leave the system prone to
soft lockups if bottom half gets very busy.

It was reproced with a set of firewall rules that REJECTed packets. If
the NIC bottom half handler ends up running on the same CPU that is
running the garbage collector on a very large cache, the garbage
collector will not be able to do its job due to the amount of work
needed for handling the REJECTs and also won't reschedule.

The fix is to disable bottom half during the garbage collecting, as it
already was in the first place (most calls to it came from softirqs).

Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ipv4: avoid parallel route cache gc executions 2014-11-05T20:27:47+00:00 Marcelo Ricardo Leitner mleitner@redhat.com 2014-08-14T19:44:53+00:00 ad5ca98f54c3b6604a7bb72059973a85deb0b779 When rt_intern_hash() has to deal with neighbour cache overflowing, it triggers the route cache garbage collector in an attempt to free some references on neighbour entries. Such call cannot be done async but should also not run in parallel with an already-running one, so that they don't collapse fighting over the hash lock entries. This patch thus blocks parallel executions with spinlocks: - A call from worker and from rt_intern_hash() are not the same, and cannot be merged, thus they will wait each other on rt_gc_lock. - Calls to gc from rt_intern_hash() may happen in parallel but we must wait for it to finish in order to try again. This dedup and synchrinozation is then performed by the locking just before calling __do_rt_garbage_collect(). Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
When rt_intern_hash() has to deal with neighbour cache overflowing,
it triggers the route cache garbage collector in an attempt to free
some references on neighbour entries.

Such call cannot be done async but should also not run in parallel with
an already-running one, so that they don't collapse fighting over the
hash lock entries.

This patch thus blocks parallel executions with spinlocks:
- A call from worker and from rt_intern_hash() are not the same, and
cannot be merged, thus they will wait each other on rt_gc_lock.
- Calls to gc from rt_intern_hash() may happen in parallel but we must
wait for it to finish in order to try again. This dedup and
synchrinozation is then performed by the locking just before calling
__do_rt_garbage_collect().

Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ipv4: move route garbage collector to work queue 2014-11-05T20:27:46+00:00 Marcelo Ricardo Leitner mleitner@redhat.com 2014-08-14T19:44:52+00:00 6c383b3a565dbf07cf6665e5da535f8668479453 Currently the route garbage collector gets called by dst_alloc() if it have more entries than the threshold. But it's an expensive call, that don't really need to be done by then. Another issue with current way is that it allows running the garbage collector with the same start parameters on multiple CPUs at once, which is not optimal. A system may even soft lockup if the cache is big enough as the garbage collectors will be fighting over the hash lock entries. This patch thus moves the garbage collector to run asynchronously on a work queue, much similar to how rt_expire_check runs. There is one condition left that allows multiple executions, which is handled by the next patch. Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
Currently the route garbage collector gets called by dst_alloc() if it
have more entries than the threshold. But it's an expensive call, that
don't really need to be done by then.

Another issue with current way is that it allows running the garbage
collector with the same start parameters on multiple CPUs at once, which
is not optimal. A system may even soft lockup if the cache is big enough
as the garbage collectors will be fighting over the hash lock entries.

This patch thus moves the garbage collector to run asynchronously on a
work queue, much similar to how rt_expire_check runs.

There is one condition left that allows multiple executions, which is
handled by the next patch.

Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
tcp: Fix integer-overflow in TCP vegas 2014-09-13T22:41:48+00:00 Christoph Paasch christoph.paasch@uclouvain.be 2014-07-29T11:40:57+00:00 4cdcdfdbf5fef2cf38167be0c366259ad768e286 [ Upstream commit 1f74e613ded11517db90b2bd57e9464d9e0fb161 ] In vegas we do a multiplication of the cwnd and the rtt. This may overflow and thus their result is stored in a u64. However, we first need to cast the cwnd so that actually 64-bit arithmetic is done. Then, we need to do do_div to allow this to be used on 32-bit arches. Cc: Stephen Hemminger <stephen@networkplumber.org> Cc: Neal Cardwell <ncardwell@google.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: David Laight <David.Laight@ACULAB.COM> Cc: Doug Leith <doug.leith@nuim.ie> Fixes: 8d3a564da34e (tcp: tcp_vegas cong avoid fix) Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
[ Upstream commit 1f74e613ded11517db90b2bd57e9464d9e0fb161 ]

In vegas we do a multiplication of the cwnd and the rtt. This
may overflow and thus their result is stored in a u64. However, we first
need to cast the cwnd so that actually 64-bit arithmetic is done.

Then, we need to do do_div to allow this to be used on 32-bit arches.

Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Doug Leith <doug.leith@nuim.ie>
Fixes: 8d3a564da34e (tcp: tcp_vegas cong avoid fix)
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
tcp: Fix integer-overflows in TCP veno 2014-09-13T22:41:48+00:00 Christoph Paasch christoph.paasch@uclouvain.be 2014-07-29T10:07:27+00:00 a16f7f29b9f02d0eda37675fb01d8d6aa54e892d [ Upstream commit 45a07695bc64b3ab5d6d2215f9677e5b8c05a7d0 ] In veno we do a multiplication of the cwnd and the rtt. This may overflow and thus their result is stored in a u64. However, we first need to cast the cwnd so that actually 64-bit arithmetic is done. A first attempt at fixing 76f1017757aa0 ([TCP]: TCP Veno congestion control) was made by 159131149c2 (tcp: Overflow bug in Vegas), but it failed to add the required cast in tcp_veno_cong_avoid(). Fixes: 76f1017757aa0 ([TCP]: TCP Veno congestion control) Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
[ Upstream commit 45a07695bc64b3ab5d6d2215f9677e5b8c05a7d0 ]

In veno we do a multiplication of the cwnd and the rtt. This
may overflow and thus their result is stored in a u64. However, we first
need to cast the cwnd so that actually 64-bit arithmetic is done.

A first attempt at fixing 76f1017757aa0 ([TCP]: TCP Veno congestion
control) was made by 159131149c2 (tcp: Overflow bug in Vegas), but it
failed to add the required cast in tcp_veno_cong_avoid().

Fixes: 76f1017757aa0 ([TCP]: TCP Veno congestion control)
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ip: make IP identifiers less predictable 2014-09-13T22:41:48+00:00 Eric Dumazet edumazet@google.com 2014-07-26T06:58:10+00:00 bf63acfdbf5c15e482a0b31043d666f3d3b1cf30 [ Upstream commit 04ca6973f7c1a0d8537f2d9906a0cf8e69886d75 ] In "Counting Packets Sent Between Arbitrary Internet Hosts", Jeffrey and Jedidiah describe ways exploiting linux IP identifier generation to infer whether two machines are exchanging packets. With commit 73f156a6e8c1 ("inetpeer: get rid of ip_id_count"), we changed IP id generation, but this does not really prevent this side-channel technique. This patch adds a random amount of perturbation so that IP identifiers for a given destination [1] are no longer monotonically increasing after an idle period. Note that prandom_u32_max(1) returns 0, so if generator is used at most once per jiffy, this patch inserts no hole in the ID suite and do not increase collision probability. This is jiffies based, so in the worst case (HZ=1000), the id can rollover after ~65 seconds of idle time, which should be fine. We also change the hash used in __ip_select_ident() to not only hash on daddr, but also saddr and protocol, so that ICMP probes can not be used to infer information for other protocols. For IPv6, adds saddr into the hash as well, but not nexthdr. If I ping the patched target, we can see ID are now hard to predict. 21:57:11.008086 IP (...) A > target: ICMP echo request, seq 1, length 64 21:57:11.010752 IP (... id 2081 ...) target > A: ICMP echo reply, seq 1, length 64 21:57:12.013133 IP (...) A > target: ICMP echo request, seq 2, length 64 21:57:12.015737 IP (... id 3039 ...) target > A: ICMP echo reply, seq 2, length 64 21:57:13.016580 IP (...) A > target: ICMP echo request, seq 3, length 64 21:57:13.019251 IP (... id 3437 ...) target > A: ICMP echo reply, seq 3, length 64 [1] TCP sessions uses a per flow ID generator not changed by this patch. Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Jeffrey Knockel <jeffk@cs.unm.edu> Reported-by: Jedidiah R. Crandall <crandall@cs.unm.edu> Cc: Willy Tarreau <w@1wt.eu> Cc: Hannes Frederic Sowa <hannes@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
[ Upstream commit 04ca6973f7c1a0d8537f2d9906a0cf8e69886d75 ]

In "Counting Packets Sent Between Arbitrary Internet Hosts", Jeffrey and
Jedidiah describe ways exploiting linux IP identifier generation to
infer whether two machines are exchanging packets.

With commit 73f156a6e8c1 ("inetpeer: get rid of ip_id_count"), we
changed IP id generation, but this does not really prevent this
side-channel technique.

This patch adds a random amount of perturbation so that IP identifiers
for a given destination [1] are no longer monotonically increasing after
an idle period.

Note that prandom_u32_max(1) returns 0, so if generator is used at most
once per jiffy, this patch inserts no hole in the ID suite and do not
increase collision probability.

This is jiffies based, so in the worst case (HZ=1000), the id can
rollover after ~65 seconds of idle time, which should be fine.

We also change the hash used in __ip_select_ident() to not only hash
on daddr, but also saddr and protocol, so that ICMP probes can not be
used to infer information for other protocols.

For IPv6, adds saddr into the hash as well, but not nexthdr.

If I ping the patched target, we can see ID are now hard to predict.

21:57:11.008086 IP (...)
    A > target: ICMP echo request, seq 1, length 64
21:57:11.010752 IP (... id 2081 ...)
    target > A: ICMP echo reply, seq 1, length 64

21:57:12.013133 IP (...)
    A > target: ICMP echo request, seq 2, length 64
21:57:12.015737 IP (... id 3039 ...)
    target > A: ICMP echo reply, seq 2, length 64

21:57:13.016580 IP (...)
    A > target: ICMP echo request, seq 3, length 64
21:57:13.019251 IP (... id 3437 ...)
    target > A: ICMP echo reply, seq 3, length 64

[1] TCP sessions uses a per flow ID generator not changed by this patch.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Jeffrey Knockel <jeffk@cs.unm.edu>
Reported-by: Jedidiah R. Crandall <crandall@cs.unm.edu>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Hannes Frederic Sowa <hannes@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
inetpeer: get rid of ip_id_count 2014-09-13T22:41:48+00:00 Eric Dumazet edumazet@google.com 2014-06-02T12:26:03+00:00 64b5c251d5b2cee4a0f697bfb90d79263f6dd517 [ Upstream commit 73f156a6e8c1074ac6327e0abd1169e95eb66463 ] Ideally, we would need to generate IP ID using a per destination IP generator. linux kernels used inet_peer cache for this purpose, but this had a huge cost on servers disabling MTU discovery. 1) each inet_peer struct consumes 192 bytes 2) inetpeer cache uses a binary tree of inet_peer structs, with a nominal size of ~66000 elements under load. 3) lookups in this tree are hitting a lot of cache lines, as tree depth is about 20. 4) If server deals with many tcp flows, we have a high probability of not finding the inet_peer, allocating a fresh one, inserting it in the tree with same initial ip_id_count, (cf secure_ip_id()) 5) We garbage collect inet_peer aggressively. IP ID generation do not have to be 'perfect' Goal is trying to avoid duplicates in a short period of time, so that reassembly units have a chance to complete reassembly of fragments belonging to one message before receiving other fragments with a recycled ID. We simply use an array of generators, and a Jenkin hash using the dst IP as a key. ipv6_select_ident() is put back into net/ipv6/ip6_output.c where it belongs (it is only used from this file) secure_ip_id() and secure_ipv6_id() no longer are needed. Rename ip_select_ident_more() to ip_select_ident_segs() to avoid unnecessary decrement/increment of the number of segments. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
[ Upstream commit 73f156a6e8c1074ac6327e0abd1169e95eb66463 ]

Ideally, we would need to generate IP ID using a per destination IP
generator.

linux kernels used inet_peer cache for this purpose, but this had a huge
cost on servers disabling MTU discovery.

1) each inet_peer struct consumes 192 bytes

2) inetpeer cache uses a binary tree of inet_peer structs,
   with a nominal size of ~66000 elements under load.

3) lookups in this tree are hitting a lot of cache lines, as tree depth
   is about 20.

4) If server deals with many tcp flows, we have a high probability of
   not finding the inet_peer, allocating a fresh one, inserting it in
   the tree with same initial ip_id_count, (cf secure_ip_id())

5) We garbage collect inet_peer aggressively.

IP ID generation do not have to be 'perfect'

Goal is trying to avoid duplicates in a short period of time,
so that reassembly units have a chance to complete reassembly of
fragments belonging to one message before receiving other fragments
with a recycled ID.

We simply use an array of generators, and a Jenkin hash using the dst IP
as a key.

ipv6_select_ident() is put back into net/ipv6/ip6_output.c where it
belongs (it is only used from this file)

secure_ip_id() and secure_ipv6_id() no longer are needed.

Rename ip_select_ident_more() to ip_select_ident_segs() to avoid
unnecessary decrement/increment of the number of segments.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
netlabel: fix a problem when setting bits below the previously lowest bit 2014-09-13T22:41:42+00:00 Paul Moore pmoore@redhat.com 2014-08-01T15:17:03+00:00 33401ce96ad0b9ba39a5aff56ef25c63859f347d commit 41c3bd2039e0d7b3dc32313141773f20716ec524 upstream. The NetLabel category (catmap) functions have a problem in that they assume categories will be set in an increasing manner, e.g. the next category set will always be larger than the last. Unfortunately, this is not a valid assumption and could result in problems when attempting to set categories less than the startbit in the lowest catmap node. In some cases kernel panics and other nasties can result. This patch corrects the problem by checking for this and allocating a new catmap node instance and placing it at the front of the list. Reported-by: Christian Evans <frodox@zoho.com> Signed-off-by: Paul Moore <pmoore@redhat.com> Tested-by: Casey Schaufler <casey@schaufler-ca.com> [bwh: Backported to 3.2: adjust filename for SMACK] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 41c3bd2039e0d7b3dc32313141773f20716ec524 upstream.

The NetLabel category (catmap) functions have a problem in that they
assume categories will be set in an increasing manner, e.g. the next
category set will always be larger than the last.  Unfortunately, this
is not a valid assumption and could result in problems when attempting
to set categories less than the startbit in the lowest catmap node.
In some cases kernel panics and other nasties can result.

This patch corrects the problem by checking for this and allocating a
new catmap node instance and placing it at the front of the list.

Reported-by: Christian Evans <frodox@zoho.com>
Signed-off-by: Paul Moore <pmoore@redhat.com>
Tested-by: Casey Schaufler <casey@schaufler-ca.com>
[bwh: Backported to 3.2: adjust filename for SMACK]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
netfilter: ipt_ULOG: fix info leaks 2014-08-06T17:07:40+00:00 Mathias Krause minipli@googlemail.com 2013-09-30T20:05:08+00:00 0368fea2438c346e753aa37606688c421ba11c4b commit 278f2b3e2af5f32ea1afe34fa12a2518153e6e49 upstream. The ulog messages leak heap bytes by the means of padding bytes and incompletely filled string arrays. Fix those by memset(0)'ing the whole struct before filling it. Signed-off-by: Mathias Krause <minipli@googlemail.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 278f2b3e2af5f32ea1afe34fa12a2518153e6e49 upstream.

The ulog messages leak heap bytes by the means of padding bytes and
incompletely filled string arrays. Fix those by memset(0)'ing the
whole struct before filling it.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ipv4: fix buffer overflow in ip_options_compile() 2014-08-06T17:07:39+00:00 Eric Dumazet edumazet@google.com 2014-07-21T05:17:42+00:00 223105654ef9efb8c040cfb91e03ce1a8de69dd0 [ Upstream commit 10ec9472f05b45c94db3c854d22581a20b97db41 ] There is a benign buffer overflow in ip_options_compile spotted by AddressSanitizer[1] : Its benign because we always can access one extra byte in skb->head (because header is followed by struct skb_shared_info), and in this case this byte is not even used. [28504.910798] ================================================================== [28504.912046] AddressSanitizer: heap-buffer-overflow in ip_options_compile [28504.913170] Read of size 1 by thread T15843: [28504.914026] [<ffffffff81802f91>] ip_options_compile+0x121/0x9c0 [28504.915394] [<ffffffff81804a0d>] ip_options_get_from_user+0xad/0x120 [28504.916843] [<ffffffff8180dedf>] do_ip_setsockopt.isra.15+0x8df/0x1630 [28504.918175] [<ffffffff8180ec60>] ip_setsockopt+0x30/0xa0 [28504.919490] [<ffffffff8181e59b>] tcp_setsockopt+0x5b/0x90 [28504.920835] [<ffffffff8177462f>] sock_common_setsockopt+0x5f/0x70 [28504.922208] [<ffffffff817729c2>] SyS_setsockopt+0xa2/0x140 [28504.923459] [<ffffffff818cfb69>] system_call_fastpath+0x16/0x1b [28504.924722] [28504.925106] Allocated by thread T15843: [28504.925815] [<ffffffff81804995>] ip_options_get_from_user+0x35/0x120 [28504.926884] [<ffffffff8180dedf>] do_ip_setsockopt.isra.15+0x8df/0x1630 [28504.927975] [<ffffffff8180ec60>] ip_setsockopt+0x30/0xa0 [28504.929175] [<ffffffff8181e59b>] tcp_setsockopt+0x5b/0x90 [28504.930400] [<ffffffff8177462f>] sock_common_setsockopt+0x5f/0x70 [28504.931677] [<ffffffff817729c2>] SyS_setsockopt+0xa2/0x140 [28504.932851] [<ffffffff818cfb69>] system_call_fastpath+0x16/0x1b [28504.934018] [28504.934377] The buggy address ffff880026382828 is located 0 bytes to the right [28504.934377] of 40-byte region [ffff880026382800, ffff880026382828) [28504.937144] [28504.937474] Memory state around the buggy address: [28504.938430] ffff880026382300: ........ rrrrrrrr rrrrrrrr rrrrrrrr [28504.939884] ffff880026382400: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr [28504.941294] ffff880026382500: .....rrr rrrrrrrr rrrrrrrr rrrrrrrr [28504.942504] ffff880026382600: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr [28504.943483] ffff880026382700: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr [28504.944511] >ffff880026382800: .....rrr rrrrrrrr rrrrrrrr rrrrrrrr [28504.945573] ^ [28504.946277] ffff880026382900: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr [28505.094949] ffff880026382a00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr [28505.096114] ffff880026382b00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr [28505.097116] ffff880026382c00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr [28505.098472] ffff880026382d00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr [28505.099804] Legend: [28505.100269] f - 8 freed bytes [28505.100884] r - 8 redzone bytes [28505.101649] . - 8 allocated bytes [28505.102406] x=1..7 - x allocated bytes + (8-x) redzone bytes [28505.103637] ================================================================== [1] https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerForKernel Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
[ Upstream commit 10ec9472f05b45c94db3c854d22581a20b97db41 ]

There is a benign buffer overflow in ip_options_compile spotted by
AddressSanitizer[1] :

Its benign because we always can access one extra byte in skb->head
(because header is followed by struct skb_shared_info), and in this case
this byte is not even used.

[28504.910798] ==================================================================
[28504.912046] AddressSanitizer: heap-buffer-overflow in ip_options_compile
[28504.913170] Read of size 1 by thread T15843:
[28504.914026]  [<ffffffff81802f91>] ip_options_compile+0x121/0x9c0
[28504.915394]  [<ffffffff81804a0d>] ip_options_get_from_user+0xad/0x120
[28504.916843]  [<ffffffff8180dedf>] do_ip_setsockopt.isra.15+0x8df/0x1630
[28504.918175]  [<ffffffff8180ec60>] ip_setsockopt+0x30/0xa0
[28504.919490]  [<ffffffff8181e59b>] tcp_setsockopt+0x5b/0x90
[28504.920835]  [<ffffffff8177462f>] sock_common_setsockopt+0x5f/0x70
[28504.922208]  [<ffffffff817729c2>] SyS_setsockopt+0xa2/0x140
[28504.923459]  [<ffffffff818cfb69>] system_call_fastpath+0x16/0x1b
[28504.924722]
[28504.925106] Allocated by thread T15843:
[28504.925815]  [<ffffffff81804995>] ip_options_get_from_user+0x35/0x120
[28504.926884]  [<ffffffff8180dedf>] do_ip_setsockopt.isra.15+0x8df/0x1630
[28504.927975]  [<ffffffff8180ec60>] ip_setsockopt+0x30/0xa0
[28504.929175]  [<ffffffff8181e59b>] tcp_setsockopt+0x5b/0x90
[28504.930400]  [<ffffffff8177462f>] sock_common_setsockopt+0x5f/0x70
[28504.931677]  [<ffffffff817729c2>] SyS_setsockopt+0xa2/0x140
[28504.932851]  [<ffffffff818cfb69>] system_call_fastpath+0x16/0x1b
[28504.934018]
[28504.934377] The buggy address ffff880026382828 is located 0 bytes to the right
[28504.934377]  of 40-byte region [ffff880026382800, ffff880026382828)
[28504.937144]
[28504.937474] Memory state around the buggy address:
[28504.938430]  ffff880026382300: ........ rrrrrrrr rrrrrrrr rrrrrrrr
[28504.939884]  ffff880026382400: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28504.941294]  ffff880026382500: .....rrr rrrrrrrr rrrrrrrr rrrrrrrr
[28504.942504]  ffff880026382600: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28504.943483]  ffff880026382700: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28504.944511] >ffff880026382800: .....rrr rrrrrrrr rrrrrrrr rrrrrrrr
[28504.945573]                         ^
[28504.946277]  ffff880026382900: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.094949]  ffff880026382a00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.096114]  ffff880026382b00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.097116]  ffff880026382c00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.098472]  ffff880026382d00: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
[28505.099804] Legend:
[28505.100269]  f - 8 freed bytes
[28505.100884]  r - 8 redzone bytes
[28505.101649]  . - 8 allocated bytes
[28505.102406]  x=1..7 - x allocated bytes + (8-x) redzone bytes
[28505.103637] ==================================================================

[1] https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerForKernel

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>