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btrfs: convert extent_map.refs from atomic_t to refcount_t

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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: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Elena Reshetova 2017-03-03 10:55:12 +02:00 committed by David Sterba
parent 9b64f57ddf
commit 490b54d6fb
6 changed files with 12 additions and 11 deletions
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4
fs/btrfs/extent_io.c
View File

@ -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;

10
fs/btrfs/extent_map.c
View File

@ -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;
}

3
fs/btrfs/extent_map.h
View File

@ -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;
};

2
fs/btrfs/tree-log.c
View File

@ -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++;

2
fs/btrfs/volumes.c
View File

@ -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) {

2
include/trace/events/btrfs.h
View File

@ -213,7 +213,7 @@ TRACE_EVENT_CONDITION(btrfs_get_extent,
__entry->block_start = map->block_start;
__entry->block_len = map->block_len;
__entry->flags = map->flags;
__entry->refs = atomic_read(&map->refs);
__entry->refs = refcount_read(&map->refs);
__entry->compress_type = map->compress_type;
),