linux-ext4 - [PATCH 1/1] ext4: better error handling of kstrdup()

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Message-Id: <1426886514-23522-1-git-send-email-tsgatesv@gmail.com>
Date:	Fri, 20 Mar 2015 17:21:54 -0400
From:	Taesoo Kim <tsgatesv@...il.com>
To:	tytso@....edu, adilger.kernel@...ger.ca,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	taesoo@...ech.edu, changwoo@...ech.edu, sanidhya@...ech.edu,
	blee@...ech.edu, csong84@...ech.edu,
	Taesoo Kim <tsgatesv@...il.com>
Subject: [PATCH 1/1] ext4: better error handling of kstrdup()

Upon memory pressure, kstrdup() might fail and correctly
handle memory error, although current implementation do not
refer orig_data.

NOTE. fortunately the correct impl works, other than a
corner case where kstrdup() fails and kzalloc() succeeds;
it might record 'NULL' in the log.

Signed-off-by: Taesoo Kim <tsgatesv@...il.com>
---
 fs/ext4/super.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e061e66..e2a609c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3408,7 +3408,7 @@ static int ext4_reserve_clusters(struct ext4_sb_info *sbi, ext4_fsblk_t count)

 static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 {
-	char *orig_data = kstrdup(data, GFP_KERNEL);
+	char *orig_data;
 	struct buffer_head *bh;
 	struct ext4_super_block *es = NULL;
 	struct ext4_sb_info *sbi;
@@ -3431,6 +3431,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 	ext4_group_t first_not_zeroed;

+	orig_data = kstrdup(data, GFP_KERNEL);
+	if (!orig_data)
+		return -ENOMEM;
+
 	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
 	if (!sbi)
 		goto out_free_orig;
@@ -4843,6 +4847,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	int i, j;
 #endif
 	char *orig_data = kstrdup(data, GFP_KERNEL);
+	if (!orig_data)
+		return -ENOMEM;

 	/* Store the original options */
 	old_sb_flags = sb->s_flags;
--
2.3.3

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