diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-02-22 13:05:30 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-02-22 13:05:30 -0800 |
| commit | 250a25e7a1d71da06213aa354ece44fb8faa73f7 (patch) | |
| tree | 53bce39e79d1501eb275b5ad3ff780f009894db1 | |
| parent | 205f92d7f2106fb248d65d2abce943ed6002598f (diff) | |
| parent | 23d8f5b684fc30126b7708cad38b753eaa078b3e (diff) | |
Merge branch 'work.audit' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
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()
| -rw-r--r-- | fs/dcache.c | 25 | ||||
| -rw-r--r-- | include/linux/dcache.h | 2 | ||||
| -rw-r--r-- | security/lsm_audit.c | 5 |
3 files changed, 30 insertions, 2 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index c17fd15b01d4..799d9e4f0bcd 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1044,6 +1044,31 @@ 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. */ diff --git a/include/linux/dcache.h b/include/linux/dcache.h index d7b369fc15d3..c1e48014106f 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -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 *); diff --git a/security/lsm_audit.c b/security/lsm_audit.c index a0cd28cd31a8..82ce14933513 100644 --- a/security/lsm_audit.c +++ b/security/lsm_audit.c @@ -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: { |