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Date:   Mon, 26 Oct 2020 20:09:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jan Kara <jack@...e.cz>, Andreas Dilger <adilger@...ger.ca>,
        Ritesh Harjani <riteshh@...ux.ibm.com>,
        Theodore Ts'o <tytso@....edu>, Sasha Levin <sashal@...nel.org>,
        linux-ext4@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 37/46] ext4: Detect already used quota file early

From: Jan Kara <jack@...e.cz>

[ Upstream commit e0770e91424f694b461141cbc99adf6b23006b60 ]

When we try to use file already used as a quota file again (for the same
or different quota type), strange things can happen. At the very least
lockdep annotations may be wrong but also inode flags may be wrongly set
/ reset. When the file is used for two quota types at once we can even
corrupt the file and likely crash the kernel. Catch all these cases by
checking whether passed file is already used as quota file and bail
early in that case.

This fixes occasional generic/219 failure due to lockdep complaint.

Reviewed-by: Andreas Dilger <adilger@...ger.ca>
Reported-by: Ritesh Harjani <riteshh@...ux.ibm.com>
Signed-off-by: Jan Kara <jack@...e.cz>
Link: https://lore.kernel.org/r/20201015110330.28716-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ext4/super.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 634c822d1dc98..d941b0cee5f8e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5626,6 +5626,11 @@ static int ext4_quota_on(struct super_block *sb, int type, int format_id,
 	/* Quotafile not on the same filesystem? */
 	if (path->dentry->d_sb != sb)
 		return -EXDEV;
+
+	/* Quota already enabled for this file? */
+	if (IS_NOQUOTA(d_inode(path->dentry)))
+		return -EBUSY;
+
 	/* Journaling quota? */
 	if (EXT4_SB(sb)->s_qf_names[type]) {
 		/* Quotafile not in fs root? */
-- 
2.25.1

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