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Commit 490b54d6 authored by Elena Reshetova's avatar Elena Reshetova Committed by David Sterba
Browse files

btrfs: convert extent_map.refs from atomic_t to refcount_t 



refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarDavid Windsor <dwindsor@gmail.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 9b64f57d

fs/btrfs/extent_io.c

+2 −2
Original line number Diff line number Diff line
@@ -2859,7 +2859,7 @@ __get_extent_map(struct inode *inode, struct page *page, size_t pg_offset, 
		em = *em_cached;

		if (extent_map_in_tree(em) && start >= em->start &&

		    start < extent_map_end(em)) {

			atomic_inc(&em->refs);

			refcount_inc(&em->refs);

			return em;

		}
@@ -2870,7 +2870,7 @@ __get_extent_map(struct inode *inode, struct page *page, size_t pg_offset, 
	em = get_extent(BTRFS_I(inode), page, pg_offset, start, len, 0);

	if (em_cached && !IS_ERR_OR_NULL(em)) {

		BUG_ON(*em_cached);

		atomic_inc(&em->refs);

		refcount_inc(&em->refs);

		*em_cached = em;

	}

	return em;

fs/btrfs/extent_map.c

+5 −5
Original line number Diff line number Diff line
@@ -55,7 +55,7 @@ struct extent_map *alloc_extent_map(void) 
	em->flags = 0;

	em->compress_type = BTRFS_COMPRESS_NONE;

	em->generation = 0;

	atomic_set(&em->refs, 1);

	refcount_set(&em->refs, 1);

	INIT_LIST_HEAD(&em->list);

	return em;

}
@@ -71,8 +71,8 @@ void free_extent_map(struct extent_map *em) 
{

	if (!em)

		return;

	WARN_ON(atomic_read(&em->refs) == 0);

	if (atomic_dec_and_test(&em->refs)) {

	WARN_ON(refcount_read(&em->refs) == 0);

	if (refcount_dec_and_test(&em->refs)) {

		WARN_ON(extent_map_in_tree(em));

		WARN_ON(!list_empty(&em->list));

		if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
@@ -322,7 +322,7 @@ static inline void setup_extent_mapping(struct extent_map_tree *tree, 
					struct extent_map *em,

					int modified)

{

	atomic_inc(&em->refs);

	refcount_inc(&em->refs);

	em->mod_start = em->start;

	em->mod_len = em->len;
@@ -381,7 +381,7 @@ __lookup_extent_mapping(struct extent_map_tree *tree, 
	if (strict && !(end > em->start && start < extent_map_end(em)))

		return NULL;



	atomic_inc(&em->refs);

	refcount_inc(&em->refs);

	return em;

}

fs/btrfs/extent_map.h

+2 −1
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#define __EXTENTMAP__



#include <linux/rbtree.h>

#include <linux/refcount.h>



#define EXTENT_MAP_LAST_BYTE ((u64)-4)

#define EXTENT_MAP_HOLE ((u64)-3)
@@ -41,7 +42,7 @@ struct extent_map { 
		 */

		struct map_lookup *map_lookup;

	};

	atomic_t refs;

	refcount_t refs;

	unsigned int compress_type;

	struct list_head list;

};

fs/btrfs/tree-log.c

+1 −1
Original line number Diff line number Diff line
@@ -4196,7 +4196,7 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans, 
		if (em->generation <= test_gen)

			continue;

		/* Need a ref to keep it from getting evicted from cache */

		atomic_inc(&em->refs);

		refcount_inc(&em->refs);

		set_bit(EXTENT_FLAG_LOGGING, &em->flags);

		list_add_tail(&em->list, &extents);

		num++;

fs/btrfs/volumes.c

+1 −1
Original line number Diff line number Diff line
@@ -4839,7 +4839,7 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans, 
	ret = add_extent_mapping(em_tree, em, 0);

	if (!ret) {

		list_add_tail(&em->list, &trans->transaction->pending_chunks);

		atomic_inc(&em->refs);

		refcount_inc(&em->refs);

	}

	write_unlock(&em_tree->lock);

	if (ret) {