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.l...@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
--
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