[PATCH 02/17] fs, btrfs: convert btrfs_transaction.use_count from atomic_t to refcount_t

From: Elena Reshetova
Date: Fri Mar 03 2017 - 03:59:23 EST

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@xxxxxxxxx>
Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>
---
fs/btrfs/disk-io.c | 2 +-
fs/btrfs/extent-tree.c | 2 +-
fs/btrfs/ordered-data.c | 2 +-
fs/btrfs/transaction.c | 20 ++++++++++----------
fs/btrfs/transaction.h | 3 ++-
5 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 5f1b08c..dca6432 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -4615,7 +4615,7 @@ static int btrfs_cleanup_transaction(struct btrfs_fs_info *fs_info)
t = list_first_entry(&fs_info->trans_list,
struct btrfs_transaction, list);
if (t->state >= TRANS_STATE_COMMIT_START) {
- atomic_inc(&t->use_count);
+ refcount_inc(&t->use_count);
spin_unlock(&fs_info->trans_lock);
btrfs_wait_for_commit(fs_info, t->transid);
btrfs_put_transaction(t);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 6079465..63ba295 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10849,7 +10849,7 @@ static int btrfs_trim_free_extents(struct btrfs_device *device,
spin_lock(&fs_info->trans_lock);
trans = fs_info->running_transaction;
if (trans)
- atomic_inc(&trans->use_count);
+ refcount_inc(&trans->use_count);
spin_unlock(&fs_info->trans_lock);

ret = find_free_dev_extent_start(trans, device, minlen, start,
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 9a46878..da5399f 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -623,7 +623,7 @@ void btrfs_remove_ordered_extent(struct inode *inode,
spin_lock(&fs_info->trans_lock);
trans = fs_info->running_transaction;
if (trans)
- atomic_inc(&trans->use_count);
+ refcount_inc(&trans->use_count);
spin_unlock(&fs_info->trans_lock);

ASSERT(trans);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 61b807d..a7d7a7d 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -60,8 +60,8 @@ static const unsigned int btrfs_blocked_trans_types[TRANS_STATE_MAX] = {

void btrfs_put_transaction(struct btrfs_transaction *transaction)
{
- WARN_ON(atomic_read(&transaction->use_count) == 0);
- if (atomic_dec_and_test(&transaction->use_count)) {
+ WARN_ON(refcount_read(&transaction->use_count) == 0);
+ if (refcount_dec_and_test(&transaction->use_count)) {
BUG_ON(!list_empty(&transaction->list));
WARN_ON(!RB_EMPTY_ROOT(&transaction->delayed_refs.href_root));
if (transaction->delayed_refs.pending_csums)
@@ -207,7 +207,7 @@ static noinline int join_transaction(struct btrfs_fs_info *fs_info,
spin_unlock(&fs_info->trans_lock);
return -EBUSY;
}
- atomic_inc(&cur_trans->use_count);
+ refcount_inc(&cur_trans->use_count);
atomic_inc(&cur_trans->num_writers);
extwriter_counter_inc(cur_trans, type);
spin_unlock(&fs_info->trans_lock);
@@ -257,7 +257,7 @@ static noinline int join_transaction(struct btrfs_fs_info *fs_info,
* One for this trans handle, one so it will live on until we
* commit the transaction.
*/
- atomic_set(&cur_trans->use_count, 2);
+ refcount_set(&cur_trans->use_count, 2);
atomic_set(&cur_trans->pending_ordered, 0);
cur_trans->flags = 0;
cur_trans->start_time = get_seconds();
@@ -432,7 +432,7 @@ static void wait_current_trans(struct btrfs_fs_info *fs_info)
spin_lock(&fs_info->trans_lock);
cur_trans = fs_info->running_transaction;
if (cur_trans && is_transaction_blocked(cur_trans)) {
- atomic_inc(&cur_trans->use_count);
+ refcount_inc(&cur_trans->use_count);
spin_unlock(&fs_info->trans_lock);

wait_event(fs_info->transaction_wait,
@@ -744,7 +744,7 @@ int btrfs_wait_for_commit(struct btrfs_fs_info *fs_info, u64 transid)
list_for_each_entry(t, &fs_info->trans_list, list) {
if (t->transid == transid) {
cur_trans = t;
- atomic_inc(&cur_trans->use_count);
+ refcount_inc(&cur_trans->use_count);
ret = 0;
break;
}
@@ -773,7 +773,7 @@ int btrfs_wait_for_commit(struct btrfs_fs_info *fs_info, u64 transid)
if (t->state == TRANS_STATE_COMPLETED)
break;
cur_trans = t;
- atomic_inc(&cur_trans->use_count);
+ refcount_inc(&cur_trans->use_count);
break;
}
}
@@ -1839,7 +1839,7 @@ int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,

/* take transaction reference */
cur_trans = trans->transaction;
- atomic_inc(&cur_trans->use_count);
+ refcount_inc(&cur_trans->use_count);

btrfs_end_transaction(trans);

@@ -2015,7 +2015,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
spin_lock(&fs_info->trans_lock);
if (cur_trans->state >= TRANS_STATE_COMMIT_START) {
spin_unlock(&fs_info->trans_lock);
- atomic_inc(&cur_trans->use_count);
+ refcount_inc(&cur_trans->use_count);
ret = btrfs_end_transaction(trans);

wait_for_commit(cur_trans);
@@ -2035,7 +2035,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
prev_trans = list_entry(cur_trans->list.prev,
struct btrfs_transaction, list);
if (prev_trans->state != TRANS_STATE_COMPLETED) {
- atomic_inc(&prev_trans->use_count);
+ refcount_inc(&prev_trans->use_count);
spin_unlock(&fs_info->trans_lock);

wait_for_commit(prev_trans);
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 5dfb559..2d9ad36 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -18,6 +18,7 @@

#ifndef __BTRFS_TRANSACTION__
#define __BTRFS_TRANSACTION__
+#include <linux/refcount.h>
#include "btrfs_inode.h"
#include "delayed-ref.h"
#include "ctree.h"
@@ -49,7 +50,7 @@ struct btrfs_transaction {
* transaction can end
*/
atomic_t num_writers;
- atomic_t use_count;
+ refcount_t use_count;
atomic_t pending_ordered;

unsigned long flags;
--
2.7.4