]> git.baikalelectronics.ru Git - kernel.git/commit
ipv6: fix race condition regarding dst->expires and dst->from.
authorYOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@linux-ipv6.org>
Wed, 20 Feb 2013 00:29:08 +0000 (00:29 +0000)
committerDavid S. Miller <davem@davemloft.net>
Wed, 20 Feb 2013 20:11:45 +0000 (15:11 -0500)
commit176d9af174cdcc5005049246e3f3cc756ac40104
treec18d4c96f7e4dcf278c88e505be8225af7374800
parent8cf47d38bfa30d4e34a0e8ab64679d09c7313bea
ipv6: fix race condition regarding dst->expires and dst->from.

Eric Dumazet wrote:
| Some strange crashes happen in rt6_check_expired(), with access
| to random addresses.
|
| At first glance, it looks like the RTF_EXPIRES and
| stuff added in commit 24f78913847a4e9aa
| (ipv6: fix problem with expired dst cache)
| are racy : same dst could be manipulated at the same time
| on different cpus.
|
| At some point, our stack believes rt->dst.from contains a dst pointer,
| while its really a jiffie value (as rt->dst.expires shares the same area
| of memory)
|
| rt6_update_expires() should be fixed, or am I missing something ?
|
| CC Neil because of https://bugzilla.redhat.com/show_bug.cgi?id=892060

Because we do not have any locks for dst_entry, we cannot change
essential structure in the entry; e.g., we cannot change reference
to other entity.

To fix this issue, split 'from' and 'expires' field in dst_entry
out of union.  Once it is 'from' is assigned in the constructor,
keep the reference until the very last stage of the life time of
the object.

Of course, it is unsafe to change 'from', so make rt6_set_from simple
just for fresh entries.

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Reported-by: Neil Horman <nhorman@tuxdriver.com>
CC: Gao Feng <gaofeng@cn.fujitsu.com>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reported-by: Steinar H. Gunderson <sesse@google.com>
Reviewed-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
include/net/dst.h
include/net/ip6_fib.h
net/core/dst.c
net/ipv6/route.c