AUDIT: Avoid sleeping function in SElinux AVC audit.

This patch changes the SELinux AVC to defer logging of paths to the audit
framework upon syscall exit, by saving a reference to the (dentry,vfsmount)
pair in an auxiliary audit item on the current audit context for processing
by audit_log_exit.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

3 files changed, 51 insertions, 9 deletions

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 17ea5d522d81..4b7caf0c6e10 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -69,6 +69,7 @@
 
 #define AUDIT_AVC               1400    /* SE Linux avc denial or grant */
 #define AUDIT_SELINUX_ERR       1401    /* Internal SE Linux Errors */
+#define AUDIT_AVC_PATH          1402    /* dentry, vfsmount pair from avc */
 
 #define AUDIT_KERNEL            2000    /* Asynchronous audit record. NOT A REQUEST. */
 
@@ -225,6 +226,7 @@ extern uid_t audit_get_loginuid(struct audit_context *ctx);
 extern int audit_ipc_perms(unsigned long qbytes, uid_t uid, gid_t gid, mode_t mode);
 extern int audit_socketcall(int nargs, unsigned long *args);
 extern int audit_sockaddr(int len, void *addr);
+extern int audit_avc_path(struct dentry *dentry, struct vfsmount *mnt);
 extern void audit_signal_info(int sig, struct task_struct *t);
 #else
 #define audit_alloc(t) ({ 0; })
@@ -240,6 +242,7 @@ extern void audit_signal_info(int sig, struct task_struct *t);
 #define audit_ipc_perms(q,u,g,m) ({ 0; })
 #define audit_socketcall(n,a) ({ 0; })
 #define audit_sockaddr(len, addr) ({ 0; })
+#define audit_avc_path(dentry, mnt) ({ 0; })
 #define audit_signal_info(s,t) do { ; } while (0)
 #endif
 
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 78d7a13fc86f..8dc5b2767145 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -34,6 +34,7 @@
 #include <asm/types.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/mount.h>
 #include <linux/socket.h>
 #include <linux/audit.h>
 #include <linux/personality.h>
@@ -124,6 +125,11 @@ struct audit_aux_data_sockaddr {
         char                    a[0];
 };
 
+struct audit_aux_data_path {
+        struct audit_aux_data   d;
+        struct dentry           *dentry;
+        struct vfsmount         *mnt;
+};
 
 /* The per-task audit context. */
 struct audit_context {
@@ -553,6 +559,11 @@ static inline void audit_free_aux(struct audit_context *context)
         struct audit_aux_data *aux;
 
         while ((aux = context->aux)) {
+                if (aux->type == AUDIT_AVC_PATH) {
+                        struct audit_aux_data_path *axi = (void *)aux;
+                        dput(axi->dentry);
+                        mntput(axi->mnt);
+                }
                 context->aux = aux->next;
                 kfree(aux);
         }
@@ -724,6 +735,14 @@ static void audit_log_exit(struct audit_context *context)
                         audit_log_format(ab, "saddr=");
                         audit_log_hex(ab, axs->a, axs->len);
                         break; }
+
+                case AUDIT_AVC_PATH: {
+                        struct audit_aux_data_path *axi = (void *)aux;
+                        audit_log_d_path(ab, "path=", axi->dentry, axi->mnt);
+                        dput(axi->dentry);
+                        mntput(axi->mnt);
+                        break; }
+
                 }
                 audit_log_end(ab);
 
@@ -1124,6 +1143,27 @@ int audit_sockaddr(int len, void *a)
         return 0;
 }
 
+int audit_avc_path(struct dentry *dentry, struct vfsmount *mnt)
+{
+        struct audit_aux_data_path *ax;
+        struct audit_context *context = current->audit_context;
+
+        if (likely(!context))
+                return 0;
+
+        ax = kmalloc(sizeof(*ax), GFP_ATOMIC);
+        if (!ax)
+                return -ENOMEM;
+
+        ax->dentry = dget(dentry);
+        ax->mnt = mntget(mnt);
+
+        ax->d.type = AUDIT_AVC_PATH;
+        ax->d.next = context->aux;
+        context->aux = (void *)ax;
+        return 0;
+}
+
 void audit_signal_info(int sig, struct task_struct *t)
 {
         extern pid_t audit_sig_pid;
diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index 62b963aca275..0fbc3e98c5ea 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -573,13 +573,10 @@ void avc_audit(u32 ssid, u32 tsid,
                 case AVC_AUDIT_DATA_FS:
                         if (a->u.fs.dentry) {
                                 struct dentry *dentry = a->u.fs.dentry;
-                                if (a->u.fs.mnt) {
-                                        audit_log_d_path(ab, "path=", dentry,
-                                                        a->u.fs.mnt);
-                                } else {
-                                        audit_log_format(ab, " name=%s",
-                                                         dentry->d_name.name);
-                                }
+                                if (a->u.fs.mnt)
+                                        audit_avc_path(dentry, a->u.fs.mnt);
+                                audit_log_format(ab, " name=%s",
+                                                 dentry->d_name.name);
                                 inode = dentry->d_inode;
                         } else if (a->u.fs.inode) {
                                 struct dentry *dentry;
@@ -630,8 +627,10 @@ void avc_audit(u32 ssid, u32 tsid,
                                 case AF_UNIX:
                                         u = unix_sk(sk);
                                         if (u->dentry) {
-                                                audit_log_d_path(ab, "path=",
-                                                        u->dentry, u->mnt);
+                                                audit_avc_path(u->dentry, u->mnt);
+                                                audit_log_format(ab, " name=%s",
+                                                                 u->dentry->d_name.name);
+
                                                 break;
                                         }
                                         if (!u->addr)