[PATCH AUTOSEL 4.14 13/16] tomoyo: ignore data race while checking quota

Sasha Levin
2021-02-24T14:19:48Z

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

[ Upstream commit 5797e861e402fff2bedce4ec8b7c89f4248b6073 ]

syzbot is reporting that tomoyo's quota check is racy [1]. But this check
is tolerant of some degree of inaccuracy. Thus, teach KCSAN to ignore
this data race.

[1] https://syzkaller.appspot.com/bug?id=999533deec7ba6337f8aa25d8bd1a4d5f7e50476

Reported-by: syzbot <syzbot+0789a72b46fd91431bd8@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
security/tomoyo/file.c | 16 ++++++++--------
security/tomoyo/network.c | 8 ++++----
security/tomoyo/util.c | 24 ++++++++++++------------
3 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/security/tomoyo/file.c b/security/tomoyo/file.c
index 2a374b4da8f5c..cbe0dc87bb919 100644
--- a/security/tomoyo/file.c
+++ b/security/tomoyo/file.c
@@ -356,13 +356,13 @@ static bool tomoyo_merge_path_acl(struct tomoyo_acl_info *a,
{
u16 * const a_perm = &container_of(a, struct tomoyo_path_acl, head)
->perm;
- u16 perm = *a_perm;
+ u16 perm = READ_ONCE(*a_perm);
const u16 b_perm = container_of(b, struct tomoyo_path_acl, head)->perm;
if (is_delete)
perm &= ~b_perm;
else
perm |= b_perm;
- *a_perm = perm;
+ WRITE_ONCE(*a_perm, perm);
return !perm;
}

@@ -428,14 +428,14 @@ static bool tomoyo_merge_mkdev_acl(struct tomoyo_acl_info *a,
{
u8 *const a_perm = &container_of(a, struct tomoyo_mkdev_acl,
head)->perm;
- u8 perm = *a_perm;
+ u8 perm = READ_ONCE(*a_perm);
const u8 b_perm = container_of(b, struct tomoyo_mkdev_acl, head)
->perm;
if (is_delete)
perm &= ~b_perm;
else
perm |= b_perm;
- *a_perm = perm;
+ WRITE_ONCE(*a_perm, perm);
return !perm;
}

@@ -505,13 +505,13 @@ static bool tomoyo_merge_path2_acl(struct tomoyo_acl_info *a,
{
u8 * const a_perm = &container_of(a, struct tomoyo_path2_acl, head)
->perm;
- u8 perm = *a_perm;
+ u8 perm = READ_ONCE(*a_perm);
const u8 b_perm = container_of(b, struct tomoyo_path2_acl, head)->perm;
if (is_delete)
perm &= ~b_perm;
else
perm |= b_perm;
- *a_perm = perm;
+ WRITE_ONCE(*a_perm, perm);
return !perm;
}

@@ -640,14 +640,14 @@ static bool tomoyo_merge_path_number_acl(struct tomoyo_acl_info *a,
{
u8 * const a_perm = &container_of(a, struct tomoyo_path_number_acl,
head)->perm;
- u8 perm = *a_perm;
+ u8 perm = READ_ONCE(*a_perm);
const u8 b_perm = container_of(b, struct tomoyo_path_number_acl, head)
->perm;
if (is_delete)
perm &= ~b_perm;
else
perm |= b_perm;
- *a_perm = perm;
+ WRITE_ONCE(*a_perm, perm);
return !perm;
}

diff --git a/security/tomoyo/network.c b/security/tomoyo/network.c
index cd6932e5225c4..828645fc97c09 100644
--- a/security/tomoyo/network.c
+++ b/security/tomoyo/network.c
@@ -233,14 +233,14 @@ static bool tomoyo_merge_inet_acl(struct tomoyo_acl_info *a,
{
u8 * const a_perm =
&container_of(a, struct tomoyo_inet_acl, head)->perm;
- u8 perm = *a_perm;
+ u8 perm = READ_ONCE(*a_perm);
const u8 b_perm = container_of(b, struct tomoyo_inet_acl, head)->perm;

if (is_delete)
perm &= ~b_perm;
else
perm |= b_perm;
- *a_perm = perm;
+ WRITE_ONCE(*a_perm, perm);
return !perm;
}

@@ -259,14 +259,14 @@ static bool tomoyo_merge_unix_acl(struct tomoyo_acl_info *a,
{
u8 * const a_perm =
&container_of(a, struct tomoyo_unix_acl, head)->perm;
- u8 perm = *a_perm;
+ u8 perm = READ_ONCE(*a_perm);
const u8 b_perm = container_of(b, struct tomoyo_unix_acl, head)->perm;

if (is_delete)
perm &= ~b_perm;
else
perm |= b_perm;
- *a_perm = perm;
+ WRITE_ONCE(*a_perm, perm);
return !perm;
}

diff --git a/security/tomoyo/util.c b/security/tomoyo/util.c
index 580b318910f14..f512123c7753d 100644
--- a/security/tomoyo/util.c
+++ b/security/tomoyo/util.c
@@ -1041,30 +1041,30 @@ bool tomoyo_domain_quota_is_ok(struct tomoyo_request_info *r)
u8 i;
if (ptr->is_deleted)
continue;
+ /*
+ * Reading perm bitmap might race with tomoyo_merge_*() because
+ * caller does not hold tomoyo_policy_lock mutex. But exceeding
+ * max_learning_entry parameter by a few entries does not harm.
+ */
switch (ptr->type) {
case TOMOYO_TYPE_PATH_ACL:
- perm = container_of(ptr, struct tomoyo_path_acl, head)
- ->perm;
+ data_race(perm = container_of(ptr, struct tomoyo_path_acl, head)->perm);
break;
case TOMOYO_TYPE_PATH2_ACL:
- perm = container_of(ptr, struct tomoyo_path2_acl, head)
- ->perm;
+ data_race(perm = container_of(ptr, struct tomoyo_path2_acl, head)->perm);
break;
case TOMOYO_TYPE_PATH_NUMBER_ACL:
- perm = container_of(ptr, struct tomoyo_path_number_acl,
- head)->perm;
+ data_race(perm = container_of(ptr, struct tomoyo_path_number_acl, head)
+ ->perm);
break;
case TOMOYO_TYPE_MKDEV_ACL:
- perm = container_of(ptr, struct tomoyo_mkdev_acl,
- head)->perm;
+ data_race(perm = container_of(ptr, struct tomoyo_mkdev_acl, head)->perm);
break;
case TOMOYO_TYPE_INET_ACL:
- perm = container_of(ptr, struct tomoyo_inet_acl,
- head)->perm;
+ data_race(perm = container_of(ptr, struct tomoyo_inet_acl, head)->perm);
break;
case TOMOYO_TYPE_UNIX_ACL:
- perm = container_of(ptr, struct tomoyo_unix_acl,
- head)->perm;
+ data_race(perm = container_of(ptr, struct tomoyo_unix_acl, head)->perm);
break;
case TOMOYO_TYPE_MANUAL_TASK_ACL:
perm = 0;
--
2.27.0