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Date: Thu, 17 Mar 2022 16:47:57 +0100
From: Jan Kara <jack@...e.cz>
To: Ye Bin <yebin10@...wei.com>
Cc: tytso@....edu, adilger.kernel@...ger.ca,
linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
jack@...e.cz, lczerner@...hat.com
Subject: Re: [PATCH -next v2] jbd2: Fix null-ptr-deref when process reserved
list in jbd2_journal_commit_transaction
On Thu 17-03-22 22:21:37, Ye Bin wrote:
> 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>
Thanks. Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> 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
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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