smack: pass error code through pointers

This patch makes the following functions to use ERR_PTR() and related
macros to pass the appropriate error code through returned pointers:

smk_parse_smack()
smk_import_entry()
smk_fetch()

It also makes all the other functions that use them to handle the
error cases properly. This ways correct error codes from places
where they happened can be propagated to the user space if necessary.

Doing this it fixes a bug in onlycap and unconfined files
handling. Previously their content was cleared on any error from
smk_import_entry/smk_parse_smack, be it EINVAL (as originally intended)
or ENOMEM. Right now it only reacts on EINVAL passing other codes
properly to userspace.

Comments have been updated accordingly.

Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@samsung.com>

1 files changed, 54 insertions, 39 deletions

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index f09b8c7cf1e7..a143328f75eb 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -245,8 +245,8 @@ static int smk_bu_credfile(const struct cred *cred, struct file *file,
  * @ip: a pointer to the inode
  * @dp: a pointer to the dentry
  *
- * Returns a pointer to the master list entry for the Smack label
- * or NULL if there was no label to fetch.
+ * Returns a pointer to the master list entry for the Smack label,
+ * NULL if there was no label to fetch, or an error code.
  */
 static struct smack_known *smk_fetch(const char *name, struct inode *ip,
 					struct dentry *dp)
@@ -256,14 +256,18 @@ static struct smack_known *smk_fetch(const char *name, struct inode *ip,
 	struct smack_known *skp = NULL;
 
 	if (ip->i_op->getxattr == NULL)
-		return NULL;
+		return ERR_PTR(-EOPNOTSUPP);
 
 	buffer = kzalloc(SMK_LONGLABEL, GFP_KERNEL);
 	if (buffer == NULL)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	rc = ip->i_op->getxattr(dp, name, buffer, SMK_LONGLABEL);
-	if (rc > 0)
+	if (rc < 0)
+		skp = ERR_PTR(rc);
+	else if (rc == 0)
+		skp = NULL;
+	else
 		skp = smk_import_entry(buffer, rc);
 
 	kfree(buffer);
@@ -605,40 +609,44 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
 		if (strncmp(op, SMK_FSHAT, strlen(SMK_FSHAT)) == 0) {
 			op += strlen(SMK_FSHAT);
 			skp = smk_import_entry(op, 0);
-			if (skp != NULL) {
-				sp->smk_hat = skp;
-				specified = 1;
-			}
+			if (IS_ERR(skp))
+				return PTR_ERR(skp);
+			sp->smk_hat = skp;
+			specified = 1;
+
 		} else if (strncmp(op, SMK_FSFLOOR, strlen(SMK_FSFLOOR)) == 0) {
 			op += strlen(SMK_FSFLOOR);
 			skp = smk_import_entry(op, 0);
-			if (skp != NULL) {
-				sp->smk_floor = skp;
-				specified = 1;
-			}
+			if (IS_ERR(skp))
+				return PTR_ERR(skp);
+			sp->smk_floor = skp;
+			specified = 1;
+
 		} else if (strncmp(op, SMK_FSDEFAULT,
 				   strlen(SMK_FSDEFAULT)) == 0) {
 			op += strlen(SMK_FSDEFAULT);
 			skp = smk_import_entry(op, 0);
-			if (skp != NULL) {
-				sp->smk_default = skp;
-				specified = 1;
-			}
+			if (IS_ERR(skp))
+				return PTR_ERR(skp);
+			sp->smk_default = skp;
+			specified = 1;
+
 		} else if (strncmp(op, SMK_FSROOT, strlen(SMK_FSROOT)) == 0) {
 			op += strlen(SMK_FSROOT);
 			skp = smk_import_entry(op, 0);
-			if (skp != NULL) {
-				sp->smk_root = skp;
-				specified = 1;
-			}
+			if (IS_ERR(skp))
+				return PTR_ERR(skp);
+			sp->smk_root = skp;
+			specified = 1;
+
 		} else if (strncmp(op, SMK_FSTRANS, strlen(SMK_FSTRANS)) == 0) {
 			op += strlen(SMK_FSTRANS);
 			skp = smk_import_entry(op, 0);
-			if (skp != NULL) {
-				sp->smk_root = skp;
-				transmute = 1;
-				specified = 1;
-			}
+			if (IS_ERR(skp))
+				return PTR_ERR(skp);
+			sp->smk_root = skp;
+			transmute = 1;
+			specified = 1;
 		}
 	}
 
@@ -1118,7 +1126,9 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
 
 	if (rc == 0 && check_import) {
 		skp = size ? smk_import_entry(value, size) : NULL;
-		if (skp == NULL || (check_star &&
+		if (IS_ERR(skp))
+			rc = PTR_ERR(skp);
+		else if (skp == NULL || (check_star &&
 		    (skp == &smack_known_star || skp == &smack_known_web)))
 			rc = -EINVAL;
 	}
@@ -1158,19 +1168,19 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name,
 
 	if (strcmp(name, XATTR_NAME_SMACK) == 0) {
 		skp = smk_import_entry(value, size);
-		if (skp != NULL)
+		if (!IS_ERR(skp))
 			isp->smk_inode = skp;
 		else
 			isp->smk_inode = &smack_known_invalid;
 	} else if (strcmp(name, XATTR_NAME_SMACKEXEC) == 0) {
 		skp = smk_import_entry(value, size);
-		if (skp != NULL)
+		if (!IS_ERR(skp))
 			isp->smk_task = skp;
 		else
 			isp->smk_task = &smack_known_invalid;
 	} else if (strcmp(name, XATTR_NAME_SMACKMMAP) == 0) {
 		skp = smk_import_entry(value, size);
-		if (skp != NULL)
+		if (!IS_ERR(skp))
 			isp->smk_mmap = skp;
 		else
 			isp->smk_mmap = &smack_known_invalid;
@@ -2403,8 +2413,8 @@ static int smack_inode_setsecurity(struct inode *inode, const char *name,
 		return -EINVAL;
 
 	skp = smk_import_entry(value, size);
-	if (skp == NULL)
-		return -EINVAL;
+	if (IS_ERR(skp))
+		return PTR_ERR(skp);
 
 	if (strcmp(name, XATTR_SMACK_SUFFIX) == 0) {
 		nsp->smk_inode = skp;
@@ -3177,7 +3187,7 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 		 */
 		dp = dget(opt_dentry);
 		skp = smk_fetch(XATTR_NAME_SMACK, inode, dp);
-		if (skp != NULL)
+		if (!IS_ERR_OR_NULL(skp))
 			final = skp;
 
 		/*
@@ -3214,11 +3224,14 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 		 * Don't let the exec or mmap label be "*" or "@".
 		 */
 		skp = smk_fetch(XATTR_NAME_SMACKEXEC, inode, dp);
-		if (skp == &smack_known_star || skp == &smack_known_web)
+		if (IS_ERR(skp) || skp == &smack_known_star ||
+		    skp == &smack_known_web)
 			skp = NULL;
 		isp->smk_task = skp;
+
 		skp = smk_fetch(XATTR_NAME_SMACKMMAP, inode, dp);
-		if (skp == &smack_known_star || skp == &smack_known_web)
+		if (IS_ERR(skp) || skp == &smack_known_star ||
+		    skp == &smack_known_web)
 			skp = NULL;
 		isp->smk_mmap = skp;
 
@@ -3302,8 +3315,8 @@ static int smack_setprocattr(struct task_struct *p, char *name,
 		return -EINVAL;
 
 	skp = smk_import_entry(value, size);
-	if (skp == NULL)
-		return -EINVAL;
+	if (IS_ERR(skp))
+		return PTR_ERR(skp);
 
 	/*
 	 * No process is ever allowed the web ("@") label.
@@ -4078,8 +4091,10 @@ static int smack_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
 		return -EINVAL;
 
 	skp = smk_import_entry(rulestr, 0);
-	if (skp)
-		*rule = skp->smk_known;
+	if (IS_ERR(skp))
+		return PTR_ERR(skp);
+
+	*rule = skp->smk_known;
 
 	return 0;
 }