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Message-ID: <20220317142137.1821590-1-yebin10@huawei.com>
Date: Thu, 17 Mar 2022 22:21:37 +0800
From: Ye Bin <yebin10@...wei.com>
To: <tytso@....edu>, <adilger.kernel@...ger.ca>,
<linux-ext4@...r.kernel.org>
CC: <linux-kernel@...r.kernel.org>, <jack@...e.cz>,
<lczerner@...hat.com>, Ye Bin <yebin10@...wei.com>
Subject: [PATCH -next v2] jbd2: Fix null-ptr-deref when process reserved list in jbd2_journal_commit_transaction
we got issue as follows:
[ 72.796117] EXT4-fs error (device sda): ext4_journal_check_start:83: comm fallocate: Detected aborted journal
[ 72.826847] EXT4-fs (sda): Remounting filesystem read-only
fallocate: fallocate failed: Read-only file system
[ 74.791830] jbd2_journal_commit_transaction: jh=0xffff9cfefe725d90 bh=0x0000000000000000 end delay
[ 74.793597] ------------[ cut here ]------------
[ 74.794203] kernel BUG at fs/jbd2/transaction.c:2063!
[ 74.794886] invalid opcode: 0000 [#1] PREEMPT SMP PTI
[ 74.795533] CPU: 4 PID: 2260 Comm: jbd2/sda-8 Not tainted 5.17.0-rc8-next-20220315-dirty #150
[ 74.798327] RIP: 0010:__jbd2_journal_unfile_buffer+0x3e/0x60
[ 74.801971] RSP: 0018:ffffa828c24a3cb8 EFLAGS: 00010202
[ 74.802694] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 74.803601] RDX: 0000000000000001 RSI: ffff9cfefe725d90 RDI: ffff9cfefe725d90
[ 74.804554] RBP: ffff9cfefe725d90 R08: 0000000000000000 R09: ffffa828c24a3b20
[ 74.805471] R10: 0000000000000001 R11: 0000000000000001 R12: ffff9cfefe725d90
[ 74.806385] R13: ffff9cfefe725d98 R14: 0000000000000000 R15: ffff9cfe833a4d00
[ 74.807301] FS: 0000000000000000(0000) GS:ffff9d01afb00000(0000) knlGS:0000000000000000
[ 74.808338] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 74.809084] CR2: 00007f2b81bf4000 CR3: 0000000100056000 CR4: 00000000000006e0
[ 74.810047] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 74.810981] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 74.811897] Call Trace:
[ 74.812241] <TASK>
[ 74.812566] __jbd2_journal_refile_buffer+0x12f/0x180
[ 74.813246] jbd2_journal_refile_buffer+0x4c/0xa0
[ 74.813869] jbd2_journal_commit_transaction.cold+0xa1/0x148
[ 74.817550] kjournald2+0xf8/0x3e0
[ 74.819056] kthread+0x153/0x1c0
[ 74.819963] ret_from_fork+0x22/0x30
Above issue may happen as follows:
write truncate kjournald2
generic_perform_write
ext4_write_begin
ext4_walk_page_buffers
do_journal_get_write_access ->add BJ_Reserved list
ext4_journalled_write_end
ext4_walk_page_buffers
write_end_fn
ext4_handle_dirty_metadata
***************JBD2 ABORT**************
jbd2_journal_dirty_metadata
-> return -EROFS, jh in reserved_list
jbd2_journal_commit_transaction
while (commit_transaction->t_reserved_list)
jh = commit_transaction->t_reserved_list;
truncate_pagecache_range
do_invalidatepage
ext4_journalled_invalidatepage
jbd2_journal_invalidatepage
journal_unmap_buffer
__dispose_buffer
__jbd2_journal_unfile_buffer
jbd2_journal_put_journal_head ->put last ref_count
__journal_remove_journal_head
bh->b_private = NULL;
jh->b_bh = NULL;
jbd2_journal_refile_buffer(journal, jh);
bh = jh2bh(jh);
->bh is NULL, later will trigger null-ptr-deref
journal_free_journal_head(jh);
As after 96f1e0974575 commit, handle reserved list will not hold "journal->j_state_lock"
when kjournald2 commit transaction. So journal_unmap_buffer maybe free
journal_head when handle reserved list. And lead to null-ptr-deref or some
strange errors.
As reserved list almost time is empty. Use "journal->j_state_lock" to protect
handle reserved list can simply solve above issue.
Fixes: 96f1e0974575("jbd2: avoid long hold times of j_state_lock while committing a transaction")
Signed-off-by: Ye Bin <yebin10@...wei.com>
---
fs/jbd2/commit.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 5b9408e3b370..ac7f067b7bdd 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -488,7 +488,6 @@ void jbd2_journal_commit_transaction(journal_t *journal)
jbd2_journal_wait_updates(journal);
commit_transaction->t_state = T_SWITCH;
- write_unlock(&journal->j_state_lock);
J_ASSERT (atomic_read(&commit_transaction->t_outstanding_credits) <=
journal->j_max_transaction_buffers);
@@ -508,6 +507,8 @@ void jbd2_journal_commit_transaction(journal_t *journal)
* has reserved. This is consistent with the existing behaviour
* that multiple jbd2_journal_get_write_access() calls to the same
* buffer are perfectly permissible.
+ * We use journal->j_state_lock here to serialize processing of
+ * t_reserved_list with eviction of buffers from journal_unmap_buffer().
*/
while (commit_transaction->t_reserved_list) {
jh = commit_transaction->t_reserved_list;
@@ -527,6 +528,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
jbd2_journal_refile_buffer(journal, jh);
}
+ write_unlock(&journal->j_state_lock);
/*
* Now try to drop any written-back buffers from the journal's
* checkpoint lists. We do this *before* commit because it potentially
--
2.31.1
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