linux-ext4 - [PATCH v2] jbd2: preserve original nofs flag during journal restart

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20170517161629.15170-1-tahsin@google.com>
Date:   Wed, 17 May 2017 09:16:29 -0700
From:   Tahsin Erdogan <tahsin@...gle.com>
To:     Michal Hocko <mhocko@...e.com>, Theodore Ts'o <tytso@....edu>,
        Jan Kara <jack@...e.com>
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tahsin Erdogan <tahsin@...gle.com>
Subject: [PATCH v2] jbd2: preserve original nofs flag during journal restart

When a transaction starts, start_this_handle() saves current
PF_MEMALLOC_NOFS value so that it can be restored at journal stop time.
Journal restart is a special case that calls start_this_handle() without
stopping the transaction. start_this_handle() isn't aware that the
original value is already stored so it overwrites it with current value.

For instance, a call sequence like below leaves PF_MEMALLOC_NOFS flag set
at the end:

  jbd2_journal_start()
  jbd2__journal_restart()
  jbd2_journal_stop()

Make jbd2__journal_restart() restore the original value before calling
start_this_handle().

Fixes: 81378da64de6 ("jbd2: mark the transaction context with the scope GFP_NOFS context")
Signed-off-by: Tahsin Erdogan <tahsin@...gle.com>
Reviewed-by: Jan Kara <jack@...e.cz>
---
v2: added comment to jbd2__journal_restart()

 fs/jbd2/transaction.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 9ee4832b6f8b..05c0323493fb 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -680,6 +680,8 @@ int jbd2__journal_restart(handle_t *handle, int nblocks, gfp_t gfp_mask)

 	rwsem_release(&journal->j_trans_commit_map, 1, _THIS_IP_);
 	handle->h_buffer_credits = nblocks;
+	/* Restore original nofs flag as jbd2_journal_stop() would do. */
+	memalloc_nofs_restore(handle->saved_alloc_context);
 	ret = start_this_handle(journal, handle, gfp_mask);
 	return ret;
 }
-- 
2.13.0.303.g4ebf302169-goog