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btrfs: convert btrfs_delayed_ref_node.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 10:55:15 +02:00 committed by David Sterba
parent 1e4f4714d5
commit 6df8cdf5bd
5 changed files with 14 additions and 12 deletions
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2
fs/btrfs/backref.c
View File

@ -1286,7 +1286,7 @@ again:
head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
if (head) {
if (!mutex_trylock(&head->mutex)) {
atomic_inc(&head->node.refs);
refcount_inc(&head->node.refs);
spin_unlock(&delayed_refs->lock);
btrfs_release_path(path);

8
fs/btrfs/delayed-ref.c
View File

@ -164,7 +164,7 @@ int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
if (mutex_trylock(&head->mutex))
return 0;
atomic_inc(&head->node.refs);
refcount_inc(&head->node.refs);
spin_unlock(&delayed_refs->lock);
mutex_lock(&head->mutex);
@ -590,7 +590,7 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info,
delayed_refs = &trans->transaction->delayed_refs;
/* first set the basic ref node struct up */
atomic_set(&ref->refs, 1);
refcount_set(&ref->refs, 1);
ref->bytenr = bytenr;
ref->num_bytes = num_bytes;
ref->ref_mod = count_mod;
@ -682,7 +682,7 @@ add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
delayed_refs = &trans->transaction->delayed_refs;
/* first set the basic ref node struct up */
atomic_set(&ref->refs, 1);
refcount_set(&ref->refs, 1);
ref->bytenr = bytenr;
ref->num_bytes = num_bytes;
ref->ref_mod = 1;
@ -739,7 +739,7 @@ add_delayed_data_ref(struct btrfs_fs_info *fs_info,
seq = atomic64_read(&fs_info->tree_mod_seq);
/* first set the basic ref node struct up */
atomic_set(&ref->refs, 1);
refcount_set(&ref->refs, 1);
ref->bytenr = bytenr;
ref->num_bytes = num_bytes;
ref->ref_mod = 1;

8
fs/btrfs/delayed-ref.h
View File

@ -18,6 +18,8 @@
#ifndef __DELAYED_REF__
#define __DELAYED_REF__
#include <linux/refcount.h>
/* these are the possible values of struct btrfs_delayed_ref_node->action */
#define BTRFS_ADD_DELAYED_REF 1 /* add one backref to the tree */
#define BTRFS_DROP_DELAYED_REF 2 /* delete one backref from the tree */
@ -53,7 +55,7 @@ struct btrfs_delayed_ref_node {
u64 seq;
/* ref count on this data structure */
atomic_t refs;
refcount_t refs;
/*
* how many refs is this entry adding or deleting. For
@ -220,8 +222,8 @@ btrfs_free_delayed_extent_op(struct btrfs_delayed_extent_op *op)
static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
{
WARN_ON(atomic_read(&ref->refs) == 0);
if (atomic_dec_and_test(&ref->refs)) {
WARN_ON(refcount_read(&ref->refs) == 0);
if (refcount_dec_and_test(&ref->refs)) {
WARN_ON(ref->in_tree);
switch (ref->type) {
case BTRFS_TREE_BLOCK_REF_KEY:

2
fs/btrfs/disk-io.c
View File

@ -4343,7 +4343,7 @@ static int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
head = rb_entry(node, struct btrfs_delayed_ref_head,
href_node);
if (!mutex_trylock(&head->mutex)) {
atomic_inc(&head->node.refs);
refcount_inc(&head->node.refs);
spin_unlock(&delayed_refs->lock);
mutex_lock(&head->mutex);

6
fs/btrfs/extent-tree.c
View File

@ -892,7 +892,7 @@ search_again:
head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
if (head) {
if (!mutex_trylock(&head->mutex)) {
atomic_inc(&head->node.refs);
refcount_inc(&head->node.refs);
spin_unlock(&delayed_refs->lock);
btrfs_release_path(path);
@ -2980,7 +2980,7 @@ again:
struct btrfs_delayed_ref_node *ref;
ref = &head->node;
atomic_inc(&ref->refs);
refcount_inc(&ref->refs);
spin_unlock(&delayed_refs->lock);
/*
@ -3057,7 +3057,7 @@ static noinline int check_delayed_ref(struct btrfs_root *root,
}
if (!mutex_trylock(&head->mutex)) {
atomic_inc(&head->node.refs);
refcount_inc(&head->node.refs);
spin_unlock(&delayed_refs->lock);
btrfs_release_path(path);