SELinux: fix sleeping allocation in security_context_to_sid

Fix a sleeping function called from invalid context bug by moving allocation
to the callers prior to taking the policy rdlock.

Signed-off-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index b86ac9d..2d5e5a3 100644 (file)
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -730,15 +730,16 @@ int security_sid_to_context_force(u32 sid, char **scontext, u32 *scontext_len)
        return security_sid_to_context_core(sid, scontext, scontext_len, 1);
 }
 
+/*
+ * Caveat:  Mutates scontext.
+ */
 static int string_to_context_struct(struct policydb *pol,
                                    struct sidtab *sidtabp,
-                                   const char *scontext,
+                                   char *scontext,
                                    u32 scontext_len,
                                    struct context *ctx,
-                                   u32 def_sid,
-                                   gfp_t gfp_flags)
+                                   u32 def_sid)
 {
-       char *scontext2 = NULL;
        struct role_datum *role;
        struct type_datum *typdatum;
        struct user_datum *usrdatum;
@@ -747,19 +748,10 @@ static int string_to_context_struct(struct policydb *pol,
 
        context_init(ctx);
 
-       /* Copy the string so that we can modify the copy as we parse it. */
-       scontext2 = kmalloc(scontext_len+1, gfp_flags);
-       if (!scontext2) {
-               rc = -ENOMEM;
-               goto out;
-       }
-       memcpy(scontext2, scontext, scontext_len);
-       scontext2[scontext_len] = 0;
-
        /* Parse the security context. */
 
        rc = -EINVAL;
-       scontextp = (char *) scontext2;
+       scontextp = (char *) scontext;
 
        /* Extract the user. */
        p = scontextp;
@@ -809,7 +801,7 @@ static int string_to_context_struct(struct policydb *pol,
        if (rc)
                goto out;
 
-       if ((p - scontext2) < scontext_len) {
+       if ((p - scontext) < scontext_len) {
                rc = -EINVAL;
                goto out;
        }
@@ -822,7 +814,6 @@ static int string_to_context_struct(struct policydb *pol,
        }
        rc = 0;
 out:
-       kfree(scontext2);
        return rc;
 }
 
@@ -830,6 +821,7 @@ static int security_context_to_sid_core(const char *scontext, u32 scontext_len,
                                        u32 *sid, u32 def_sid, gfp_t gfp_flags,
                                        int force)
 {
+       char *scontext2, *str = NULL;
        struct context context;
        int rc = 0;
 
@@ -839,27 +831,38 @@ static int security_context_to_sid_core(const char *scontext, u32 scontext_len,
                for (i = 1; i < SECINITSID_NUM; i++) {
                        if (!strcmp(initial_sid_to_string[i], scontext)) {
                                *sid = i;
-                               goto out;
+                               return 0;
                        }
                }
                *sid = SECINITSID_KERNEL;
-               goto out;
+               return 0;
        }
        *sid = SECSID_NULL;
 
+       /* Copy the string so that we can modify the copy as we parse it. */
+       scontext2 = kmalloc(scontext_len+1, gfp_flags);
+       if (!scontext2)
+               return -ENOMEM;
+       memcpy(scontext2, scontext, scontext_len);
+       scontext2[scontext_len] = 0;
+
+       if (force) {
+               /* Save another copy for storing in uninterpreted form */
+               str = kstrdup(scontext2, gfp_flags);
+               if (!str) {
+                       kfree(scontext2);
+                       return -ENOMEM;
+               }
+       }
+
        POLICY_RDLOCK;
        rc = string_to_context_struct(&policydb, &sidtab,
-                                     scontext, scontext_len,
-                                     &context, def_sid, gfp_flags);
+                                     scontext2, scontext_len,
+                                     &context, def_sid);
        if (rc == -EINVAL && force) {
-               context.str = kmalloc(scontext_len+1, gfp_flags);
-               if (!context.str) {
-                       rc = -ENOMEM;
-                       goto out;
-               }
-               memcpy(context.str, scontext, scontext_len);
-               context.str[scontext_len] = 0;
+               context.str = str;
                context.len = scontext_len;
+               str = NULL;
        } else if (rc)
                goto out;
        rc = sidtab_context_to_sid(&sidtab, &context, sid);
@@ -867,6 +870,8 @@ static int security_context_to_sid_core(const char *scontext, u32 scontext_len,
                context_destroy(&context);
 out:
        POLICY_RDUNLOCK;
+       kfree(scontext2);
+       kfree(str);
        return rc;
 }
 
@@ -1339,9 +1344,14 @@ static int convert_context(u32 key,
 
        if (c->str) {
                struct context ctx;
-               rc = string_to_context_struct(args->newp, NULL, c->str,
-                                             c->len, &ctx, SECSID_NULL,
-                                             GFP_KERNEL);
+               s = kstrdup(c->str, GFP_KERNEL);
+               if (!s) {
+                       rc = -ENOMEM;
+                       goto out;
+               }
+               rc = string_to_context_struct(args->newp, NULL, s,
+                                             c->len, &ctx, SECSID_NULL);
+               kfree(s);
                if (!rc) {
                        printk(KERN_INFO
                       "SELinux:  Context %s became valid (mapped).\n",