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Code Issues Releases Wiki Activity

jbd2: fix use-after-free of transaction_t race 

jbd2_journal_wait_updates() is called with j_state_lock held. But if
there is a commit in progress, then this transaction might get committed
and freed via jbd2_journal_commit_transaction() ->
jbd2_journal_free_transaction(), when we release j_state_lock.
So check for journal->j_running_transaction everytime we release and
acquire j_state_lock to avoid use-after-free issue.

Link: https://lore.kernel.org/r/948c2fed518ae739db6a8f7f83f1d58b504f87d0.1644497105.git.ritesh.list@gmail.com
Fixes: 4f98186848 ("jbd2: refactor wait logic for transaction updates into a common function")
Cc: stable@kernel.org
Reported-and-tested-by: syzbot+afa2ca5171d93e44b348@syzkaller.appspotmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Ritesh Harjani 2022-02-10 21:07:11 +05:30 committed by Theodore Ts'o
parent e3952fcce1
commit cc16eecae6
1 changed files with 25 additions and 16 deletions
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41
fs/jbd2/transaction.c
View File

@ -842,27 +842,38 @@ EXPORT_SYMBOL(jbd2_journal_restart);
*/
void jbd2_journal_wait_updates(journal_t *journal)
{
transaction_t *commit_transaction = journal->j_running_transaction;
DEFINE_WAIT(wait);
if (!commit_transaction)
return;
while (1) {
/*
* Note that the running transaction can get freed under us if
* this transaction is getting committed in
* jbd2_journal_commit_transaction() ->
* jbd2_journal_free_transaction(). This can only happen when we
* release j_state_lock -> schedule() -> acquire j_state_lock.
* Hence we should everytime retrieve new j_running_transaction
* value (after j_state_lock release acquire cycle), else it may
* lead to use-after-free of old freed transaction.
*/
transaction_t *transaction = journal->j_running_transaction;
spin_lock(&commit_transaction->t_handle_lock);
while (atomic_read(&commit_transaction->t_updates)) {
DEFINE_WAIT(wait);
if (!transaction)
break;
spin_lock(&transaction->t_handle_lock);
prepare_to_wait(&journal->j_wait_updates, &wait,
TASK_UNINTERRUPTIBLE);
if (atomic_read(&commit_transaction->t_updates)) {
spin_unlock(&commit_transaction->t_handle_lock);
write_unlock(&journal->j_state_lock);
schedule();
write_lock(&journal->j_state_lock);
spin_lock(&commit_transaction->t_handle_lock);
TASK_UNINTERRUPTIBLE);
if (!atomic_read(&transaction->t_updates)) {
spin_unlock(&transaction->t_handle_lock);
finish_wait(&journal->j_wait_updates, &wait);
break;
}
spin_unlock(&transaction->t_handle_lock);
write_unlock(&journal->j_state_lock);
schedule();
finish_wait(&journal->j_wait_updates, &wait);
write_lock(&journal->j_state_lock);
}
spin_unlock(&commit_transaction->t_handle_lock);
}
/**
@ -877,8 +888,6 @@ void jbd2_journal_wait_updates(journal_t *journal)
*/
void jbd2_journal_lock_updates(journal_t *journal)
{
DEFINE_WAIT(wait);
jbd2_might_wait_for_commit(journal);
write_lock(&journal->j_state_lock);