gfp flags for security_inode_alloc()?

Dave Chinner wrote:
> Yes, because you have no idea what the calling context is except
> for the fact that is from somewhere inside filesystem code and the
> filesystem could be holding locks. Therefore, GFP_NOFS is really the
> only really safe way to allocate memory here.

I see. Thank you.

I'm not sure, but can call trace happen where somewhere inside network
filesystem or stackable filesystem code with locks held invokes operations that
involves GFP_KENREL memory allocation outside that filesystem?
----------
[PATCH] SMACK: Fix incorrect GFP_KERNEL usage.

new_inode_smack() which can be called from smack_inode_alloc_security() needs
to use GFP_NOFS like SELinux's inode_alloc_security() does, for
security_inode_alloc() is called from inode_init_always() and
inode_init_always() is called from xfs_inode_alloc() which is using GFP_NOFS.

smack_inode_init_security() needs to use GFP_NOFS like
selinux_inode_init_security() does, for initxattrs() callback function (e.g.
btrfs_initxattrs()) which is called from security_inode_init_security() is
using GFP_NOFS.

smack_audit_rule_match() needs to use GFP_ATOMIC, for
security_audit_rule_match() can be called from audit_filter_user_rules() and
audit_filter_user_rules() is called from audit_filter_user() with RCU read lock
held.

Signed-off-by: Tetsuo Handa <[email protected]>
Signed-off-by: Casey Schaufler <cschaufler@cschaufler-intel.(none)>

security/smack/smack_lsm.c

@@ -79,7 +79,7 @@ struct inode_smack *new_inode_smack(char *smack)
 {
 	struct inode_smack *isp;
 
-	isp = kzalloc(sizeof(struct inode_smack), GFP_KERNEL);
+	isp = kzalloc(sizeof(struct inode_smack), GFP_NOFS);
 	if (isp == NULL)
 		return NULL;
 
@@ -563,7 +563,7 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 	int may;
 
 	if (name) {
-		*name = kstrdup(XATTR_SMACK_SUFFIX, GFP_KERNEL);
+		*name = kstrdup(XATTR_SMACK_SUFFIX, GFP_NOFS);
 		if (*name == NULL)
 			return -ENOMEM;
 	}
@@ -586,7 +586,7 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 			issp->smk_flags |= SMK_INODE_CHANGED;
 		}
 
-		*value = kstrdup(isp, GFP_KERNEL);
+		*value = kstrdup(isp, GFP_NOFS);
 		if (*value == NULL)
 			return -ENOMEM;
 	}
@@ -3426,7 +3426,7 @@ static int smack_audit_rule_match(u32 secid, u32 field, u32 op, void *vrule,
 	char *rule = vrule;
 
 	if (!rule) {
-		audit_log(actx, GFP_KERNEL, AUDIT_SELINUX_ERR,
+		audit_log(actx, GFP_ATOMIC, AUDIT_SELINUX_ERR,
 			  "Smack: missing rule\n");
 		return -ENOENT;
 	}