[PATCH 2/2] apparmor: fix suspicious RCU usage warning in policy.c/policy.h
From: John Johansen
Date: Sun Sep 29 2013 - 11:40:07 EST
The recent 3.12 pull request for apparmor was missing a couple rcu _protected
access modifiers. Resulting in the follow suspicious RCU usage
[ 29.804534] [ INFO: suspicious RCU usage. ]
[ 29.804539] 3.11.0+ #5 Not tainted
[ 29.804541] -------------------------------
[ 29.804545] security/apparmor/include/policy.h:363 suspicious rcu_dereference_check() usage!
[ 29.804548]
[ 29.804548] other info that might help us debug this:
[ 29.804548]
[ 29.804553]
[ 29.804553] rcu_scheduler_active = 1, debug_locks = 1
[ 29.804558] 2 locks held by apparmor_parser/1268:
[ 29.804560] #0: (sb_writers#9){.+.+.+}, at: [<ffffffff81120a4c>] file_start_write+0x27/0x29
[ 29.804576] #1: (&ns->lock){+.+.+.}, at: [<ffffffff811f5d88>] aa_replace_profiles+0x166/0x57c
[ 29.804589]
[ 29.804589] stack backtrace:
[ 29.804595] CPU: 0 PID: 1268 Comm: apparmor_parser Not tainted 3.11.0+ #5
[ 29.804599] Hardware name: ASUSTeK Computer Inc. UL50VT /UL50VT , BIOS 217 03/01/2010
[ 29.804602] 0000000000000000 ffff8800b95a1d90 ffffffff8144eb9b ffff8800b94db540
[ 29.804611] ffff8800b95a1dc0 ffffffff81087439 ffff880138cc3a18 ffff880138cc3a18
[ 29.804619] ffff8800b9464a90 ffff880138cc3a38 ffff8800b95a1df0 ffffffff811f5084
[ 29.804628] Call Trace:
[ 29.804636] [<ffffffff8144eb9b>] dump_stack+0x4e/0x82
[ 29.804642] [<ffffffff81087439>] lockdep_rcu_suspicious+0xfc/0x105
[ 29.804649] [<ffffffff811f5084>] __aa_update_replacedby+0x53/0x7f
[ 29.804655] [<ffffffff811f5408>] __replace_profile+0x11f/0x1ed
[ 29.804661] [<ffffffff811f6032>] aa_replace_profiles+0x410/0x57c
[ 29.804668] [<ffffffff811f16d4>] profile_replace+0x35/0x4c
[ 29.804674] [<ffffffff81120fa3>] vfs_write+0xad/0x113
[ 29.804680] [<ffffffff81121609>] SyS_write+0x44/0x7a
[ 29.804687] [<ffffffff8145bfd2>] system_call_fastpath+0x16/0x1b
[ 29.804691]
[ 29.804694] ===============================
[ 29.804697] [ INFO: suspicious RCU usage. ]
[ 29.804700] 3.11.0+ #5 Not tainted
[ 29.804703] -------------------------------
[ 29.804706] security/apparmor/policy.c:566 suspicious rcu_dereference_check() usage!
[ 29.804709]
[ 29.804709] other info that might help us debug this:
[ 29.804709]
[ 29.804714]
[ 29.804714] rcu_scheduler_active = 1, debug_locks = 1
[ 29.804718] 2 locks held by apparmor_parser/1268:
[ 29.804721] #0: (sb_writers#9){.+.+.+}, at: [<ffffffff81120a4c>] file_start_write+0x27/0x29
[ 29.804733] #1: (&ns->lock){+.+.+.}, at: [<ffffffff811f5d88>] aa_replace_profiles+0x166/0x57c
[ 29.804744]
[ 29.804744] stack backtrace:
[ 29.804750] CPU: 0 PID: 1268 Comm: apparmor_parser Not tainted 3.11.0+ #5
[ 29.804753] Hardware name: ASUSTeK Computer Inc. UL50VT /UL50VT , BIOS 217 03/01/2010
[ 29.804756] 0000000000000000 ffff8800b95a1d80 ffffffff8144eb9b ffff8800b94db540
[ 29.804764] ffff8800b95a1db0 ffffffff81087439 ffff8800b95b02b0 0000000000000000
[ 29.804772] ffff8800b9efba08 ffff880138cc3a38 ffff8800b95a1dd0 ffffffff811f4f94
[ 29.804779] Call Trace:
[ 29.804786] [<ffffffff8144eb9b>] dump_stack+0x4e/0x82
[ 29.804791] [<ffffffff81087439>] lockdep_rcu_suspicious+0xfc/0x105
[ 29.804798] [<ffffffff811f4f94>] aa_free_replacedby_kref+0x4d/0x62
[ 29.804804] [<ffffffff811f4f47>] ? aa_put_namespace+0x17/0x17
[ 29.804810] [<ffffffff811f4f0b>] kref_put+0x36/0x40
[ 29.804816] [<ffffffff811f5423>] __replace_profile+0x13a/0x1ed
[ 29.804822] [<ffffffff811f6032>] aa_replace_profiles+0x410/0x57c
[ 29.804829] [<ffffffff811f16d4>] profile_replace+0x35/0x4c
[ 29.804835] [<ffffffff81120fa3>] vfs_write+0xad/0x113
[ 29.804840] [<ffffffff81121609>] SyS_write+0x44/0x7a
[ 29.804847] [<ffffffff8145bfd2>] system_call_fastpath+0x16/0x1b
Reported-by: miles.lane@xxxxxxxxx
CC: paulmck@xxxxxxxxxxxxxxxxxx
Signed-off-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
---
security/apparmor/include/policy.h | 4 +++-
security/apparmor/policy.c | 3 ++-
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/security/apparmor/include/policy.h b/security/apparmor/include/policy.h
index f2d4b63..c28b0f2 100644
--- a/security/apparmor/include/policy.h
+++ b/security/apparmor/include/policy.h
@@ -360,7 +360,9 @@ static inline void aa_put_replacedby(struct aa_replacedby *p)
static inline void __aa_update_replacedby(struct aa_profile *orig,
struct aa_profile *new)
{
- struct aa_profile *tmp = rcu_dereference(orig->replacedby->profile);
+ struct aa_profile *tmp;
+ tmp = rcu_dereference_protected(orig->replacedby->profile,
+ mutex_is_locked(&orig->ns->lock));
rcu_assign_pointer(orig->replacedby->profile, aa_get_profile(new));
orig->flags |= PFLAG_INVALID;
aa_put_profile(tmp);
diff --git a/security/apparmor/policy.c b/security/apparmor/policy.c
index 6172509..345bec0 100644
--- a/security/apparmor/policy.c
+++ b/security/apparmor/policy.c
@@ -563,7 +563,8 @@ void __init aa_free_root_ns(void)
static void free_replacedby(struct aa_replacedby *r)
{
if (r) {
- aa_put_profile(rcu_dereference(r->profile));
+ /* r->profile will not be updated any more as r is dead */
+ aa_put_profile(rcu_dereference_protected(r->profile, true));
kzfree(r);
}
}
--
1.8.3.2
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