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audit_tree: Remove mark->lock locking
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Currently, audit_tree code uses mark->lock to protect against detaching
of mark from an inode. In most places it however also uses
mark->group->mark_mutex (as we need to atomically replace attached
marks) and this provides protection against mark detaching as well. So
just remove protection with mark->lock from audit tree code and replace
it with mark->group->mark_mutex protection in all the places. It
simplifies the code and gets rid of some ugly catches like calling
fsnotify_add_mark_locked() with mark->lock held (which cannot sleep only
because we hold a reference to another mark attached to the same inode).

Reviewed-by: Richard Guy Briggs <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Signed-off-by: Paul Moore <[email protected]>
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@jankara @pcmoore
jankara authored and pcmoore committed Nov 12, 2018
1 parent ea956d8 commit 9f16d2e
Showing 1 changed file with 4 additions and 20 deletions.
24 changes: 4 additions & 20 deletions kernel/audit_tree.c
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Original file line number Diff line number Diff line change
Expand Up @@ -193,7 +193,7 @@ static inline struct list_head *chunk_hash(unsigned long key)
return chunk_hash_heads + n % HASH_SIZE;
}

/* hash_lock & entry->lock is held by caller */
/* hash_lock & entry->group->mark_mutex is held by caller */
static void insert_hash(struct audit_chunk *chunk)
{
unsigned long key = chunk_to_key(chunk);
Expand Down Expand Up @@ -256,13 +256,11 @@ static void untag_chunk(struct node *p)
new = alloc_chunk(size);

mutex_lock(&entry->group->mark_mutex);
spin_lock(&entry->lock);
/*
* mark_mutex protects mark from getting detached and thus also from
* mark->connector->obj getting NULL.
*/
if (chunk->dead || !(entry->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
spin_unlock(&entry->lock);
mutex_unlock(&entry->group->mark_mutex);
if (new)
fsnotify_put_mark(&new->mark);
Expand All @@ -280,7 +278,6 @@ static void untag_chunk(struct node *p)
list_del_init(&p->list);
list_del_rcu(&chunk->hash);
spin_unlock(&hash_lock);
spin_unlock(&entry->lock);
mutex_unlock(&entry->group->mark_mutex);
fsnotify_destroy_mark(entry, audit_tree_group);
goto out;
Expand Down Expand Up @@ -323,7 +320,6 @@ static void untag_chunk(struct node *p)
list_for_each_entry(owner, &new->trees, same_root)
owner->root = new;
spin_unlock(&hash_lock);
spin_unlock(&entry->lock);
mutex_unlock(&entry->group->mark_mutex);
fsnotify_destroy_mark(entry, audit_tree_group);
fsnotify_put_mark(&new->mark); /* drop initial reference */
Expand All @@ -340,7 +336,6 @@ static void untag_chunk(struct node *p)
p->owner = NULL;
put_tree(owner);
spin_unlock(&hash_lock);
spin_unlock(&entry->lock);
mutex_unlock(&entry->group->mark_mutex);
out:
fsnotify_put_mark(entry);
Expand All @@ -360,12 +355,12 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
return -ENOSPC;
}

spin_lock(&entry->lock);
mutex_lock(&entry->group->mark_mutex);
spin_lock(&hash_lock);
if (tree->goner) {
spin_unlock(&hash_lock);
chunk->dead = 1;
spin_unlock(&entry->lock);
mutex_unlock(&entry->group->mark_mutex);
fsnotify_destroy_mark(entry, audit_tree_group);
fsnotify_put_mark(entry);
return 0;
Expand All @@ -380,7 +375,7 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
}
insert_hash(chunk);
spin_unlock(&hash_lock);
spin_unlock(&entry->lock);
mutex_unlock(&entry->group->mark_mutex);
fsnotify_put_mark(entry); /* drop initial reference */
return 0;
}
Expand Down Expand Up @@ -421,14 +416,12 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
chunk_entry = &chunk->mark;

mutex_lock(&old_entry->group->mark_mutex);
spin_lock(&old_entry->lock);
/*
* mark_mutex protects mark from getting detached and thus also from
* mark->connector->obj getting NULL.
*/
if (!(old_entry->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
/* old_entry is being shot, lets just lie */
spin_unlock(&old_entry->lock);
mutex_unlock(&old_entry->group->mark_mutex);
fsnotify_put_mark(old_entry);
fsnotify_put_mark(&chunk->mark);
Expand All @@ -437,23 +430,16 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)

if (fsnotify_add_mark_locked(chunk_entry, old_entry->connector->obj,
FSNOTIFY_OBJ_TYPE_INODE, 1)) {
spin_unlock(&old_entry->lock);
mutex_unlock(&old_entry->group->mark_mutex);
fsnotify_put_mark(chunk_entry);
fsnotify_put_mark(old_entry);
return -ENOSPC;
}

/* even though we hold old_entry->lock, this is safe since chunk_entry->lock could NEVER have been grabbed before */
spin_lock(&chunk_entry->lock);
spin_lock(&hash_lock);

/* we now hold old_entry->lock, chunk_entry->lock, and hash_lock */
if (tree->goner) {
spin_unlock(&hash_lock);
chunk->dead = 1;
spin_unlock(&chunk_entry->lock);
spin_unlock(&old_entry->lock);
mutex_unlock(&old_entry->group->mark_mutex);

fsnotify_destroy_mark(chunk_entry, audit_tree_group);
Expand Down Expand Up @@ -485,8 +471,6 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
list_add(&tree->same_root, &chunk->trees);
}
spin_unlock(&hash_lock);
spin_unlock(&chunk_entry->lock);
spin_unlock(&old_entry->lock);
mutex_unlock(&old_entry->group->mark_mutex);
fsnotify_destroy_mark(old_entry, audit_tree_group);
fsnotify_put_mark(chunk_entry); /* drop initial reference */
Expand Down

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