smack: use GFP_NOFS while holding inode_smack::smk_lock

commit e5bfad3 upstream.

inode_smack::smk_lock is taken during smack_d_instantiate(), which is
called during a filesystem transaction when creating a file on ext4.
Therefore to avoid a deadlock, all code that takes this lock must use
GFP_NOFS, to prevent memory reclaim from waiting for the filesystem
transaction to complete.

Reported-by: syzbot+0eefc1e06a77d327a056@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ebiggers

security/smack/smack_access.c

@@ -469,7 +469,7 @@ char *smk_parse_smack(const char *string, int len)
 	if (i == 0 || i >= SMK_LONGLABEL)
 		return ERR_PTR(-EINVAL);
 
-	smack = kzalloc(i + 1, GFP_KERNEL);
+	smack = kzalloc(i + 1, GFP_NOFS);
 	if (smack == NULL)
 		return ERR_PTR(-ENOMEM);
 
@@ -504,7 +504,7 @@ int smk_netlbl_mls(int level, char *catset, struct netlbl_lsm_secattr *sap,
 			if ((m & *cp) == 0)
 				continue;
 			rc = netlbl_catmap_setbit(&sap->attr.mls.cat,
-						  cat, GFP_KERNEL);
+						  cat, GFP_NOFS);
 			if (rc < 0) {
 				netlbl_catmap_free(sap->attr.mls.cat);
 				return rc;
@@ -540,7 +540,7 @@ struct smack_known *smk_import_entry(const char *string, int len)
 	if (skp != NULL)
 		goto freeout;
 
-	skp = kzalloc(sizeof(*skp), GFP_KERNEL);
+	skp = kzalloc(sizeof(*skp), GFP_NOFS);
 	if (skp == NULL) {
 		skp = ERR_PTR(-ENOMEM);
 		goto freeout;

security/smack/smack_lsm.c

@@ -270,7 +270,7 @@ static struct smack_known *smk_fetch(const char *name, struct inode *ip,
 	if (!(ip->i_opflags & IOP_XATTR))
 		return ERR_PTR(-EOPNOTSUPP);
 
-	buffer = kzalloc(SMK_LONGLABEL, GFP_KERNEL);
+	buffer = kzalloc(SMK_LONGLABEL, GFP_NOFS);
 	if (buffer == NULL)
 		return ERR_PTR(-ENOMEM);