'selinux_inode_follow_link()' can be called as part of an RCU path walk,
and is passed a 'bool rcu' parameter to indicate whether or not it is
being called from within an RCU read-side critical section.
Unfortunately, this knowledge is not propagated further and, instead,
'avc_has_perm()' unconditionally passes a flags argument of '0' to both
'avc_has_perm_noaudit()' and 'avc_audit()' which may block.
Introduce 'avc_has_perm_flags()' which can be used safely from within an
RCU read-side critical section.
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
security/selinux/avc.c | 12 +++++++-----
security/selinux/hooks.c | 5 +++--
security/selinux/include/avc.h | 12 ++++++++----
3 files changed, 18 insertions(+), 11 deletions(-)
diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index 9c183c899e92..7d99dadd24d0 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -1177,11 +1177,12 @@ inline int avc_has_perm_noaudit(struct selinux_state *state,
}
/**
- * avc_has_perm - Check permissions and perform any appropriate auditing.
+ * avc_has_perm_flags - Check permissions and perform any appropriate auditing.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
* @requested: requested permissions, interpreted based on @tclass
+ * @flags: AVC_STRICT, AVC_NONBLOCKING, or 0
* @auditdata: auxiliary audit data
*
* Check the AVC to determine whether the @requested permissions are granted
@@ -1192,17 +1193,18 @@ inline int avc_has_perm_noaudit(struct selinux_state *state,
* permissions are granted, -%EACCES if any permissions are denied, or
* another -errno upon other errors.
*/
-int avc_has_perm(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass,
- u32 requested, struct common_audit_data *auditdata)
+int avc_has_perm_flags(struct selinux_state *state, u32 ssid, u32 tsid,
+ u16 tclass, u32 requested, unsigned int flags,
+ struct common_audit_data *auditdata)
{
struct av_decision avd;
int rc, rc2;
- rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested, 0,
+ rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested, flags,
&avd);
rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
- auditdata, 0);
+ auditdata, flags);
if (rc2)
return rc2;
return rc;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9625b99e677f..0c09f59a2740 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3008,8 +3008,9 @@ static int selinux_inode_follow_link(struct dentry *dentry, struct inode *inode,
if (IS_ERR(isec))
return PTR_ERR(isec);
- return avc_has_perm(&selinux_state,
- sid, isec->sid, isec->sclass, FILE__READ, &ad);
+ return avc_has_perm_flags(&selinux_state, sid, isec->sid, isec->sclass,
+ rcu ? AVC_NONBLOCKING : 0,
+ FILE__READ, &ad);
}
static noinline int audit_inode_permission(struct inode *inode,
diff --git a/security/selinux/include/avc.h b/security/selinux/include/avc.h
index 7be0e1e90e8b..0450e1b88182 100644
--- a/security/selinux/include/avc.h
+++ b/security/selinux/include/avc.h
@@ -149,10 +149,14 @@ int avc_has_perm_noaudit(struct selinux_state *state,
unsigned flags,
struct av_decision *avd);
-int avc_has_perm(struct selinux_state *state,
- u32 ssid, u32 tsid,
- u16 tclass, u32 requested,
- struct common_audit_data *auditdata);
+int avc_has_perm_flags(struct selinux_state *state,
+ u32 ssid, u32 tsid,
+ u16 tclass, u32 requested,
+ unsigned flags,
+ struct common_audit_data *auditdata);
+
+#define avc_has_perm(state, ssid, tsid, tclass, requested, auditdata) \
+ avc_has_perm_flags(state, ssid, tsid, tclass, requested, 0, auditdata)
int avc_has_extended_perms(struct selinux_state *state,
u32 ssid, u32 tsid, u16 tclass, u32 requested,
--
2.24.0.432.g9d3f5f5b63-goog
