The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7b97d868b7ab2448859668de9222b8af43f76e78 Mon Sep 17 00:00:00 2001

From: "zhangyi (F)" yi.zhang@huawei.com Date: Tue, 9 Jun 2020 15:35:40 +0800 Subject: [PATCH] ext4, jbd2: ensure panic by fix a race between jbd2 abort and ext4 error handlers

In the ext4 filesystem with errors=panic, if one process is recording errno in the superblock when invoking jbd2_journal_abort() due to some error cases, it could be raced by another __ext4_abort() which is setting the SB_RDONLY flag but missing panic because errno has not been recorded.

jbd2_journal_commit_transaction() jbd2_journal_abort() journal->j_flags |= JBD2_ABORT; jbd2_journal_update_sb_errno() | ext4_journal_check_start() | __ext4_abort() | sb->s_flags |= SB_RDONLY; | if (!JBD2_REC_ERR) | return; journal->j_flags |= JBD2_REC_ERR;

Finally, it will no longer trigger panic because the filesystem has already been set read-only. Fix this by introduce j_abort_mutex to make sure journal abort is completed before panic, and remove JBD2_REC_ERR flag.

Fixes: 4327ba52afd03 ("ext4, jbd2: ensure entering into panic after recording an error in superblock") Signed-off-by: zhangyi (F) yi.zhang@huawei.com Reviewed-by: Jan Kara jack@suse.cz Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20200609073540.3810702-1-yi.zhang@huawei.com Signed-off-by: Theodore Ts'o tytso@mit.edu

diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 127b8efa8d54..2660a7e47eef 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -522,9 +522,6 @@ static void ext4_handle_error(struct super_block *sb) smp_wmb(); sb->s_flags |= SB_RDONLY; } else if (test_opt(sb, ERRORS_PANIC)) { - if (EXT4_SB(sb)->s_journal && - !(EXT4_SB(sb)->s_journal->j_flags & JBD2_REC_ERR)) - return; panic("EXT4-fs (device %s): panic forced after error\n", sb->s_id); } @@ -725,23 +722,20 @@ void __ext4_abort(struct super_block *sb, const char *function, va_end(args);

if (sb_rdonly(sb) == 0) { - ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only"); EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FS_ABORTED; + if (EXT4_SB(sb)->s_journal) + jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO); + + ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only"); /* * Make sure updated value of ->s_mount_flags will be visible * before ->s_flags update */ smp_wmb(); sb->s_flags |= SB_RDONLY; - if (EXT4_SB(sb)->s_journal) - jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO); } - if (test_opt(sb, ERRORS_PANIC) && !system_going_down()) { - if (EXT4_SB(sb)->s_journal && - !(EXT4_SB(sb)->s_journal->j_flags & JBD2_REC_ERR)) - return; + if (test_opt(sb, ERRORS_PANIC) && !system_going_down()) panic("EXT4-fs panic from previous error\n"); - } }

void __ext4_msg(struct super_block *sb, diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index a49d0e670ddf..e4944436e733 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -1140,6 +1140,7 @@ static journal_t *journal_init_common(struct block_device *bdev, init_waitqueue_head(&journal->j_wait_commit); init_waitqueue_head(&journal->j_wait_updates); init_waitqueue_head(&journal->j_wait_reserved); + mutex_init(&journal->j_abort_mutex); mutex_init(&journal->j_barrier); mutex_init(&journal->j_checkpoint_mutex); spin_lock_init(&journal->j_revoke_lock); @@ -1402,7 +1403,8 @@ static int jbd2_write_superblock(journal_t *journal, int write_flags) printk(KERN_ERR "JBD2: Error %d detected when updating " "journal superblock for %s.\n", ret, journal->j_devname); - jbd2_journal_abort(journal, ret); + if (!is_journal_aborted(journal)) + jbd2_journal_abort(journal, ret); }

return ret; @@ -2153,6 +2155,13 @@ void jbd2_journal_abort(journal_t *journal, int errno) { transaction_t *transaction;

+ /* + * Lock the aborting procedure until everything is done, this avoid + * races between filesystem's error handling flow (e.g. ext4_abort()), + * ensure panic after the error info is written into journal's + * superblock. + */ + mutex_lock(&journal->j_abort_mutex); /* * ESHUTDOWN always takes precedence because a file system check * caused by any other journal abort error is not required after @@ -2167,6 +2176,7 @@ void jbd2_journal_abort(journal_t *journal, int errno) journal->j_errno = errno; jbd2_journal_update_sb_errno(journal); } + mutex_unlock(&journal->j_abort_mutex); return; }

@@ -2188,10 +2198,7 @@ void jbd2_journal_abort(journal_t *journal, int errno) * layer could realise that a filesystem check is needed. */ jbd2_journal_update_sb_errno(journal); - - write_lock(&journal->j_state_lock); - journal->j_flags |= JBD2_REC_ERR; - write_unlock(&journal->j_state_lock); + mutex_unlock(&journal->j_abort_mutex); }

/** diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h index f613d8529863..d56128df2aff 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -765,6 +765,11 @@ struct journal_s */ int j_errno;

+ /** + * @j_abort_mutex: Lock the whole aborting procedure. + */ + struct mutex j_abort_mutex; + /** * @j_sb_buffer: The first part of the superblock buffer. */ @@ -1247,7 +1252,6 @@ JBD2_FEATURE_INCOMPAT_FUNCS(csum3, CSUM_V3) #define JBD2_ABORT_ON_SYNCDATA_ERR 0x040 /* Abort the journal on file * data write error in ordered * mode */ -#define JBD2_REC_ERR 0x080 /* The errno in the sb has been recorded */

/* * Function declarations for the journaling transaction and buffer