[patch 001/100] security/smack: fix oops when setting a size 0 SMACK64 xattr

[Chris Wright]

-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Etienne Basset <etienne.basset@xxxxxxxxxxxxxx>

upstream commit: 4303154e86597885bc3cbc178a48ccbc8213875f

this patch fix an oops in smack when setting a size 0 SMACK64 xattr eg  
attr -S -s SMACK64  -V '' somefile
This oops because smk_import_entry treats a 0 length as SMK_MAXLEN

Signed-off-by: Etienne Basset <etienne.basset@xxxxxxxxxxxxxx>
Reviewed-by: James Morris <jmorris@xxxxxxxxx>
Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
---
---
 security/smack/smack_lsm.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -607,6 +607,8 @@ static int smack_inode_setxattr(struct d
 	    strcmp(name, XATTR_NAME_SMACKIPOUT) == 0) {
 		if (!capable(CAP_MAC_ADMIN))
 			rc = -EPERM;
+		if (size == 0)
+			rc = -EINVAL;
 	} else
 		rc = cap_inode_setxattr(dentry, name, value, size, flags);
 
@@ -1430,7 +1432,7 @@ static int smack_inode_setsecurity(struc
 	struct socket *sock;
 	int rc = 0;
 
-	if (value == NULL || size > SMK_LABELLEN)
+	if (value == NULL || size > SMK_LABELLEN || size == 0)
 		return -EACCES;
 
 	sp = smk_import(value, size);

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