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 <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Casey Schaufler <cschaufler@cschaufler-intel.(none)>

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index df45d39..5f80075 100644 (file)
--- a/security/smack/smack_lsm.c
+++ b/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;
        }