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author | Al Viro <viro@zeniv.linux.org.uk> | 2019-02-15 20:09:35 +0000 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-03-19 13:12:41 +0100 |
commit | 345af5abca671b625cb64c0078dc37f49c1fa227 (patch) | |
tree | b9920251588f3f0e1ab1f059567e1369bf243323 /security/lsm_audit.c | |
parent | f56b3c297ca71eb780b7c5508532b9675f650355 (diff) | |
download | linux-stable-345af5abca671b625cb64c0078dc37f49c1fa227.tar.gz linux-stable-345af5abca671b625cb64c0078dc37f49c1fa227.tar.bz2 linux-stable-345af5abca671b625cb64c0078dc37f49c1fa227.zip |
missing barriers in some of unix_sock ->addr and ->path accesses
[ Upstream commit ae3b564179bfd06f32d051b9e5d72ce4b2a07c37 ]
Several u->addr and u->path users are not holding any locks in
common with unix_bind(). unix_state_lock() is useless for those
purposes.
u->addr is assign-once and *(u->addr) is fully set up by the time
we set u->addr (all under unix_table_lock). u->path is also
set in the same critical area, also before setting u->addr, and
any unix_sock with ->path filled will have non-NULL ->addr.
So setting ->addr with smp_store_release() is all we need for those
"lockless" users - just have them fetch ->addr with smp_load_acquire()
and don't even bother looking at ->path if they see NULL ->addr.
Users of ->addr and ->path fall into several classes now:
1) ones that do smp_load_acquire(u->addr) and access *(u->addr)
and u->path only if smp_load_acquire() has returned non-NULL.
2) places holding unix_table_lock. These are guaranteed that
*(u->addr) is seen fully initialized. If unix_sock is in one of the
"bound" chains, so's ->path.
3) unix_sock_destructor() using ->addr is safe. All places
that set u->addr are guaranteed to have seen all stores *(u->addr)
while holding a reference to u and unix_sock_destructor() is called
when (atomic) refcount hits zero.
4) unix_release_sock() using ->path is safe. unix_bind()
is serialized wrt unix_release() (normally - by struct file
refcount), and for the instances that had ->path set by unix_bind()
unix_release_sock() comes from unix_release(), so they are fine.
Instances that had it set in unix_stream_connect() either end up
attached to a socket (in unix_accept()), in which case the call
chain to unix_release_sock() and serialization are the same as in
the previous case, or they never get accept'ed and unix_release_sock()
is called when the listener is shut down and its queue gets purged.
In that case the listener's queue lock provides the barriers needed -
unix_stream_connect() shoves our unix_sock into listener's queue
under that lock right after having set ->path and eventual
unix_release_sock() caller picks them from that queue under the
same lock right before calling unix_release_sock().
5) unix_find_other() use of ->path is pointless, but safe -
it happens with successful lookup by (abstract) name, so ->path.dentry
is guaranteed to be NULL there.
earlier-variant-reviewed-by: "Paul E. McKenney" <paulmck@linux.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'security/lsm_audit.c')
-rw-r--r-- | security/lsm_audit.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/security/lsm_audit.c b/security/lsm_audit.c index f84001019356..33028c098ef3 100644 --- a/security/lsm_audit.c +++ b/security/lsm_audit.c @@ -321,6 +321,7 @@ static void dump_common_audit_data(struct audit_buffer *ab, if (a->u.net->sk) { struct sock *sk = a->u.net->sk; struct unix_sock *u; + struct unix_address *addr; int len = 0; char *p = NULL; @@ -351,14 +352,15 @@ static void dump_common_audit_data(struct audit_buffer *ab, #endif case AF_UNIX: u = unix_sk(sk); + addr = smp_load_acquire(&u->addr); + if (!addr) + break; if (u->path.dentry) { audit_log_d_path(ab, " path=", &u->path); break; } - if (!u->addr) - break; - len = u->addr->len-sizeof(short); - p = &u->addr->name->sun_path[0]; + len = addr->len-sizeof(short); + p = &addr->name->sun_path[0]; audit_log_format(ab, " path="); if (*p) audit_log_untrustedstring(ab, p); |