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Merge branch 'work.audit' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

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Pull RCU-safe common_lsm_audit() from Al Viro:
 "Make common_lsm_audit() non-blocking and usable from RCU pathwalk
  context.

  We don't really need to grab/drop dentry in there - rcu_read_lock() is
  enough. There's a couple of followups using that to simplify the
  logics in selinux, but those hadn't soaked in -next yet, so they'll
  have to go in next window"

* 'work.audit' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  make dump_common_audit_data() safe to be called from RCU pathwalk
  new helper: d_find_alias_rcu()
This commit is contained in:
Linus Torvalds 2021-02-22 13:05:30 -08:00
commit 250a25e7a1
3 changed files with 30 additions and 2 deletions
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25
fs/dcache.c
View File

@ -1043,6 +1043,31 @@ struct dentry *d_find_alias(struct inode *inode)
}
EXPORT_SYMBOL(d_find_alias);
/*
* Caller MUST be holding rcu_read_lock() and be guaranteed
* that inode won't get freed until rcu_read_unlock().
*/
struct dentry *d_find_alias_rcu(struct inode *inode)
{
struct hlist_head *l = &inode->i_dentry;
struct dentry *de = NULL;
spin_lock(&inode->i_lock);
// ->i_dentry and ->i_rcu are colocated, but the latter won't be
// used without having I_FREEING set, which means no aliases left
if (likely(!(inode->i_state & I_FREEING) && !hlist_empty(l))) {
if (S_ISDIR(inode->i_mode)) {
de = hlist_entry(l->first, struct dentry, d_u.d_alias);
} else {
hlist_for_each_entry(de, l, d_u.d_alias)
if (!d_unhashed(de))
break;
}
}
spin_unlock(&inode->i_lock);
return de;
}
/*
* Try to kill dentries associated with this inode.
* WARNING: you must own a reference to inode.

2
include/linux/dcache.h
View File

@ -262,6 +262,8 @@ extern void d_tmpfile(struct dentry *, struct inode *);
extern struct dentry *d_find_alias(struct inode *);
extern void d_prune_aliases(struct inode *);
extern struct dentry *d_find_alias_rcu(struct inode *);
/* test whether we have any submounts in a subdir tree */
extern int path_has_submounts(const struct path *);

5
security/lsm_audit.c
View File

@ -291,18 +291,19 @@ static void dump_common_audit_data(struct audit_buffer *ab,
struct dentry *dentry;
struct inode *inode;
rcu_read_lock();
inode = a->u.inode;
dentry = d_find_alias(inode);
dentry = d_find_alias_rcu(inode);
if (dentry) {
audit_log_format(ab, " name=");
spin_lock(&dentry->d_lock);
audit_log_untrustedstring(ab, dentry->d_name.name);
spin_unlock(&dentry->d_lock);
dput(dentry);
}
audit_log_format(ab, " dev=");
audit_log_untrustedstring(ab, inode->i_sb->s_id);
audit_log_format(ab, " ino=%lu", inode->i_ino);
rcu_read_unlock();
break;
}
case LSM_AUDIT_DATA_TASK: {