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mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-30 16:13:54 +08:00
linux-next/security
Al Viro ae3b564179 missing barriers in some of unix_sock ->addr and ->path accesses
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>
2019-02-20 20:06:28 -08:00
..
apparmor apparmor: Fix aa_label_build() error handling for failed merges 2019-02-01 08:01:39 -08:00
integrity Merge branch 'next-tpm' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-01-02 11:05:43 -08:00
keys KEYS: fix parsing invalid pkey info string 2019-01-01 13:13:19 -08:00
loadpin LoadPin: Rename boot param "enabled" to "enforce" 2018-10-18 15:29:44 -07:00
selinux selinux/stable-5.0 PR 20190115 2019-01-16 17:06:39 +12:00
smack Merge branch 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-01-05 13:25:58 -08:00
tomoyo Merge branch 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-01-05 13:25:58 -08:00
yama Yama: Check for pid death before checking ancestry 2019-01-16 12:00:56 -08:00
commoncap.c security: audit and remove any unnecessary uses of module.h 2018-12-12 14:58:51 -08:00
device_cgroup.c docs: fix broken references with multiple hints 2018-06-15 18:10:01 -03:00
inode.c security: fs: make inode explicitly non-modular 2018-12-12 14:58:51 -08:00
Kconfig treewide: surround Kconfig file paths with double quotes 2018-12-22 00:25:54 +09:00
lsm_audit.c missing barriers in some of unix_sock ->addr and ->path accesses 2019-02-20 20:06:28 -08:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
min_addr.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
security.c LSM: Check for NULL cred-security on free 2019-01-16 15:41:11 -08:00