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authorJohn Johansen <john.johansen@canonical.com>2013-10-14 11:46:27 -0700
committerJames Morris <james.l.morris@oracle.com>2013-10-16 11:54:01 +1100
commited2c7da3a40c58410508fe24e12d03e508d7ec01 (patch)
treeba2c63ad31c6128a344d47c3b3a596c5c76555bf /security
parent5cb3e91ebd0405519795f243adbfc4ed2a6fe53f (diff)
downloadlinux-ed2c7da3a40c58410508fe24e12d03e508d7ec01.tar.gz
apparmor: fix bad lock balance when introspecting policy
BugLink: http://bugs.launchpad.net/bugs/1235977 The profile introspection seq file has a locking bug when policy is viewed from a virtual root (task in a policy namespace), introspection from the real root is not affected. The test for root while (parent) { is correct for the real root, but incorrect for tasks in a policy namespace. This allows the task to walk backup the policy tree past its virtual root causing it to be unlocked before the virtual root should be in the p_stop fn. This results in the following lockdep back trace: [ 78.479744] [ BUG: bad unlock balance detected! ] [ 78.479792] 3.11.0-11-generic #17 Not tainted [ 78.479838] ------------------------------------- [ 78.479885] grep/2223 is trying to release lock (&ns->lock) at: [ 78.479952] [<ffffffff817bf3be>] mutex_unlock+0xe/0x10 [ 78.480002] but there are no more locks to release! [ 78.480037] [ 78.480037] other info that might help us debug this: [ 78.480037] 1 lock held by grep/2223: [ 78.480037] #0: (&p->lock){+.+.+.}, at: [<ffffffff812111bd>] seq_read+0x3d/0x3d0 [ 78.480037] [ 78.480037] stack backtrace: [ 78.480037] CPU: 0 PID: 2223 Comm: grep Not tainted 3.11.0-11-generic #17 [ 78.480037] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 78.480037] ffffffff817bf3be ffff880007763d60 ffffffff817b97ef ffff8800189d2190 [ 78.480037] ffff880007763d88 ffffffff810e1c6e ffff88001f044730 ffff8800189d2190 [ 78.480037] ffffffff817bf3be ffff880007763e00 ffffffff810e5bd6 0000000724fe56b7 [ 78.480037] Call Trace: [ 78.480037] [<ffffffff817bf3be>] ? mutex_unlock+0xe/0x10 [ 78.480037] [<ffffffff817b97ef>] dump_stack+0x54/0x74 [ 78.480037] [<ffffffff810e1c6e>] print_unlock_imbalance_bug+0xee/0x100 [ 78.480037] [<ffffffff817bf3be>] ? mutex_unlock+0xe/0x10 [ 78.480037] [<ffffffff810e5bd6>] lock_release_non_nested+0x226/0x300 [ 78.480037] [<ffffffff817bf2fe>] ? __mutex_unlock_slowpath+0xce/0x180 [ 78.480037] [<ffffffff817bf3be>] ? mutex_unlock+0xe/0x10 [ 78.480037] [<ffffffff810e5d5c>] lock_release+0xac/0x310 [ 78.480037] [<ffffffff817bf2b3>] __mutex_unlock_slowpath+0x83/0x180 [ 78.480037] [<ffffffff817bf3be>] mutex_unlock+0xe/0x10 [ 78.480037] [<ffffffff81376c91>] p_stop+0x51/0x90 [ 78.480037] [<ffffffff81211408>] seq_read+0x288/0x3d0 [ 78.480037] [<ffffffff811e9d9e>] vfs_read+0x9e/0x170 [ 78.480037] [<ffffffff811ea8cc>] SyS_read+0x4c/0xa0 [ 78.480037] [<ffffffff817ccc9d>] system_call_fastpath+0x1a/0x1f Signed-off-by: John Johansen <john.johansen@canonical.com> Signed-off-by: James Morris <james.l.morris@oracle.com>
Diffstat (limited to 'security')
-rw-r--r--security/apparmor/apparmorfs.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
index 95c2b2689a0..7db9954f1af 100644
--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -580,15 +580,13 @@ static struct aa_namespace *__next_namespace(struct aa_namespace *root,
/* check if the next ns is a sibling, parent, gp, .. */
parent = ns->parent;
- while (parent) {
+ while (ns != root) {
mutex_unlock(&ns->lock);
next = list_entry_next(ns, base.list);
if (!list_entry_is_head(next, &parent->sub_ns, base.list)) {
mutex_lock(&next->lock);
return next;
}
- if (parent == root)
- return NULL;
ns = parent;
parent = parent->parent;
}