* [PATCH] selinux: no recursive read_lock of policy_rwlock in security_genfs_sid()
@ 2014-06-20 17:45 Waiman Long
2014-06-20 17:49 ` Stephen Smalley
0 siblings, 1 reply; 3+ messages in thread
From: Waiman Long @ 2014-06-20 17:45 UTC (permalink / raw)
To: Paul Moore, Stephen Smalley, Eric Paris, James Morris
Cc: linux-kernel, linux-security-module, Scott J Norton, Waiman Long
With introduction of fair queued rwlock, recursive read_lock() may hang
the offending process if there is a write_lock() somewhere in between.
With recursive read_lock checking enabled, the following error was
reported:
=============================================
[ INFO: possible recursive locking detected ]
3.16.0-rc1 #2 Tainted: G E
---------------------------------------------
load_policy/708 is trying to acquire lock:
(policy_rwlock){.+.+..}, at: [<ffffffff8125b32a>] security_genfs_sid+0x3a/0x170
but task is already holding lock:
(policy_rwlock){.+.+..}, at: [<ffffffff8125b48c>] security_fs_use+0x2c/0x110
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(policy_rwlock);
lock(policy_rwlock);
This patch fixes the occurrence of recursive read_lock() of
policy_rwlock in security_genfs_sid() by adding a 5th argument to
indicate if the rwlock has been taken.
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
---
security/selinux/hooks.c | 2 +-
security/selinux/include/security.h | 2 +-
security/selinux/selinuxfs.c | 3 ++-
security/selinux/ss/services.c | 13 +++++++++----
4 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 83d06db..430035a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1248,7 +1248,7 @@ static int selinux_proc_get_sid(struct dentry *dentry,
path[1] = '/';
path++;
}
- rc = security_genfs_sid("proc", path, tclass, sid);
+ rc = security_genfs_sid("proc", path, tclass, sid, false);
}
free_page((unsigned long)buffer);
return rc;
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index ce7852c..6bc5b2f 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -180,7 +180,7 @@ int security_get_allow_unknown(void);
int security_fs_use(struct super_block *sb);
int security_genfs_sid(const char *fstype, char *name, u16 sclass,
- u32 *sid);
+ u32 *sid, int locked);
#ifdef CONFIG_NETLABEL
int security_netlbl_secattr_to_sid(struct netlbl_lsm_secattr *secattr,
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index c71737f..405799e 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -1273,7 +1273,8 @@ static int sel_make_bools(void)
goto out;
isec = (struct inode_security_struct *)inode->i_security;
- ret = security_genfs_sid("selinuxfs", page, SECCLASS_FILE, &sid);
+ ret = security_genfs_sid("selinuxfs", page, SECCLASS_FILE,
+ &sid, false);
if (ret)
goto out;
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 4bca494..2b23c2c 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2282,6 +2282,7 @@ out:
* @path: path from root of mount
* @sclass: file security class
* @sid: SID for path
+ * @locked: true if policy_rwlock taken
*
* Obtain a SID to use for a file in a filesystem that
* cannot support xattr or use a fixed labeling behavior like
@@ -2290,7 +2291,8 @@ out:
int security_genfs_sid(const char *fstype,
char *path,
u16 orig_sclass,
- u32 *sid)
+ u32 *sid,
+ int locked)
{
int len;
u16 sclass;
@@ -2301,7 +2303,8 @@ int security_genfs_sid(const char *fstype,
while (path[0] == '/' && path[1] == '/')
path++;
- read_lock(&policy_rwlock);
+ if (!locked)
+ read_lock(&policy_rwlock);
sclass = unmap_class(orig_sclass);
*sid = SECINITSID_UNLABELED;
@@ -2336,7 +2339,8 @@ int security_genfs_sid(const char *fstype,
*sid = c->sid[0];
rc = 0;
out:
- read_unlock(&policy_rwlock);
+ if (!locked)
+ read_unlock(&policy_rwlock);
return rc;
}
@@ -2370,7 +2374,8 @@ int security_fs_use(struct super_block *sb)
}
sbsec->sid = c->sid[0];
} else {
- rc = security_genfs_sid(fstype, "/", SECCLASS_DIR, &sbsec->sid);
+ rc = security_genfs_sid(fstype, "/", SECCLASS_DIR, &sbsec->sid,
+ true);
if (rc) {
sbsec->behavior = SECURITY_FS_USE_NONE;
rc = 0;
--
1.7.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] selinux: no recursive read_lock of policy_rwlock in security_genfs_sid()
2014-06-20 17:45 [PATCH] selinux: no recursive read_lock of policy_rwlock in security_genfs_sid() Waiman Long
@ 2014-06-20 17:49 ` Stephen Smalley
2014-06-20 23:37 ` Waiman Long
0 siblings, 1 reply; 3+ messages in thread
From: Stephen Smalley @ 2014-06-20 17:49 UTC (permalink / raw)
To: Waiman Long, Paul Moore, Eric Paris, James Morris
Cc: linux-kernel, linux-security-module, Scott J Norton
On 06/20/2014 01:45 PM, Waiman Long wrote:
> With introduction of fair queued rwlock, recursive read_lock() may hang
> the offending process if there is a write_lock() somewhere in between.
>
> With recursive read_lock checking enabled, the following error was
> reported:
>
> =============================================
> [ INFO: possible recursive locking detected ]
> 3.16.0-rc1 #2 Tainted: G E
> ---------------------------------------------
> load_policy/708 is trying to acquire lock:
> (policy_rwlock){.+.+..}, at: [<ffffffff8125b32a>] security_genfs_sid+0x3a/0x170
>
> but task is already holding lock:
> (policy_rwlock){.+.+..}, at: [<ffffffff8125b48c>] security_fs_use+0x2c/0x110
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(policy_rwlock);
> lock(policy_rwlock);
>
> This patch fixes the occurrence of recursive read_lock() of
> policy_rwlock in security_genfs_sid() by adding a 5th argument to
> indicate if the rwlock has been taken.
>
> Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Thanks, but I'd prefer to instead create a static helper function in
services.c that does not take the lock at all, use that function from
security_fs_use, and leave the extern function unmodified.
> ---
> security/selinux/hooks.c | 2 +-
> security/selinux/include/security.h | 2 +-
> security/selinux/selinuxfs.c | 3 ++-
> security/selinux/ss/services.c | 13 +++++++++----
> 4 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 83d06db..430035a 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1248,7 +1248,7 @@ static int selinux_proc_get_sid(struct dentry *dentry,
> path[1] = '/';
> path++;
> }
> - rc = security_genfs_sid("proc", path, tclass, sid);
> + rc = security_genfs_sid("proc", path, tclass, sid, false);
> }
> free_page((unsigned long)buffer);
> return rc;
> diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
> index ce7852c..6bc5b2f 100644
> --- a/security/selinux/include/security.h
> +++ b/security/selinux/include/security.h
> @@ -180,7 +180,7 @@ int security_get_allow_unknown(void);
> int security_fs_use(struct super_block *sb);
>
> int security_genfs_sid(const char *fstype, char *name, u16 sclass,
> - u32 *sid);
> + u32 *sid, int locked);
>
> #ifdef CONFIG_NETLABEL
> int security_netlbl_secattr_to_sid(struct netlbl_lsm_secattr *secattr,
> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
> index c71737f..405799e 100644
> --- a/security/selinux/selinuxfs.c
> +++ b/security/selinux/selinuxfs.c
> @@ -1273,7 +1273,8 @@ static int sel_make_bools(void)
> goto out;
>
> isec = (struct inode_security_struct *)inode->i_security;
> - ret = security_genfs_sid("selinuxfs", page, SECCLASS_FILE, &sid);
> + ret = security_genfs_sid("selinuxfs", page, SECCLASS_FILE,
> + &sid, false);
> if (ret)
> goto out;
>
> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
> index 4bca494..2b23c2c 100644
> --- a/security/selinux/ss/services.c
> +++ b/security/selinux/ss/services.c
> @@ -2282,6 +2282,7 @@ out:
> * @path: path from root of mount
> * @sclass: file security class
> * @sid: SID for path
> + * @locked: true if policy_rwlock taken
> *
> * Obtain a SID to use for a file in a filesystem that
> * cannot support xattr or use a fixed labeling behavior like
> @@ -2290,7 +2291,8 @@ out:
> int security_genfs_sid(const char *fstype,
> char *path,
> u16 orig_sclass,
> - u32 *sid)
> + u32 *sid,
> + int locked)
> {
> int len;
> u16 sclass;
> @@ -2301,7 +2303,8 @@ int security_genfs_sid(const char *fstype,
> while (path[0] == '/' && path[1] == '/')
> path++;
>
> - read_lock(&policy_rwlock);
> + if (!locked)
> + read_lock(&policy_rwlock);
>
> sclass = unmap_class(orig_sclass);
> *sid = SECINITSID_UNLABELED;
> @@ -2336,7 +2339,8 @@ int security_genfs_sid(const char *fstype,
> *sid = c->sid[0];
> rc = 0;
> out:
> - read_unlock(&policy_rwlock);
> + if (!locked)
> + read_unlock(&policy_rwlock);
> return rc;
> }
>
> @@ -2370,7 +2374,8 @@ int security_fs_use(struct super_block *sb)
> }
> sbsec->sid = c->sid[0];
> } else {
> - rc = security_genfs_sid(fstype, "/", SECCLASS_DIR, &sbsec->sid);
> + rc = security_genfs_sid(fstype, "/", SECCLASS_DIR, &sbsec->sid,
> + true);
> if (rc) {
> sbsec->behavior = SECURITY_FS_USE_NONE;
> rc = 0;
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] selinux: no recursive read_lock of policy_rwlock in security_genfs_sid()
2014-06-20 17:49 ` Stephen Smalley
@ 2014-06-20 23:37 ` Waiman Long
0 siblings, 0 replies; 3+ messages in thread
From: Waiman Long @ 2014-06-20 23:37 UTC (permalink / raw)
To: Stephen Smalley
Cc: Paul Moore, Eric Paris, James Morris, linux-kernel,
linux-security-module, Scott J Norton
On 06/20/2014 01:49 PM, Stephen Smalley wrote:
> On 06/20/2014 01:45 PM, Waiman Long wrote:
>> With introduction of fair queued rwlock, recursive read_lock() may hang
>> the offending process if there is a write_lock() somewhere in between.
>>
>> With recursive read_lock checking enabled, the following error was
>> reported:
>>
>> =============================================
>> [ INFO: possible recursive locking detected ]
>> 3.16.0-rc1 #2 Tainted: G E
>> ---------------------------------------------
>> load_policy/708 is trying to acquire lock:
>> (policy_rwlock){.+.+..}, at: [<ffffffff8125b32a>] security_genfs_sid+0x3a/0x170
>>
>> but task is already holding lock:
>> (policy_rwlock){.+.+..}, at: [<ffffffff8125b48c>] security_fs_use+0x2c/0x110
>>
>> other info that might help us debug this:
>> Possible unsafe locking scenario:
>>
>> CPU0
>> ----
>> lock(policy_rwlock);
>> lock(policy_rwlock);
>>
>> This patch fixes the occurrence of recursive read_lock() of
>> policy_rwlock in security_genfs_sid() by adding a 5th argument to
>> indicate if the rwlock has been taken.
>>
>> Signed-off-by: Waiman Long<Waiman.Long@hp.com>
> Thanks, but I'd prefer to instead create a static helper function in
> services.c that does not take the lock at all, use that function from
> security_fs_use, and leave the extern function unmodified.
On second thought, this is exactly what I want to change the patch. I
will send out a new one later today.
-Longman
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-06-20 23:37 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2014-06-20 17:45 [PATCH] selinux: no recursive read_lock of policy_rwlock in security_genfs_sid() Waiman Long
2014-06-20 17:49 ` Stephen Smalley
2014-06-20 23:37 ` Waiman Long
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox