linux-kernel - [PATCH 3.19.y-ckt 95/99] hpfs: fix remount failure when there are no options changed

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Date:	Thu,  7 Jul 2016 11:38:34 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Mikulas Patocka <mpatocka@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 95/99] hpfs: fix remount failure when there are no options changed

3.19.8-ckt23 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Mikulas Patocka <mikulas@...bright.com>

commit 44d51706b4685f965cd32acde3fe0fcc1e6198e8 upstream.

Commit ce657611baf9 ("hpfs: kstrdup() out of memory handling") checks if
the kstrdup function returns NULL due to out-of-memory condition.

However, if we are remounting a filesystem with no change to
filesystem-specific options, the parameter data is NULL.  In this case,
kstrdup returns NULL (because it was passed NULL parameter), although no
out of memory condition exists.  The mount syscall then fails with
ENOMEM.

This patch fixes the bug.  We fail with ENOMEM only if data is non-NULL.

The patch also changes the call to replace_mount_options - if we didn't
pass any filesystem-specific options, we don't call
replace_mount_options (thus we don't erase existing reported options).

Fixes: ce657611baf9 ("hpfs: kstrdup() out of memory handling")
Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 fs/hpfs/super.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/hpfs/super.c b/fs/hpfs/super.c
index 8685c65..03b2c9c 100644
--- a/fs/hpfs/super.c
+++ b/fs/hpfs/super.c
@@ -428,7 +428,7 @@ static int hpfs_remount_fs(struct super_block *s, int *flags, char *data)
 	struct hpfs_sb_info *sbi = hpfs_sb(s);
 	char *new_opts = kstrdup(data, GFP_KERNEL);

-	if (!new_opts)
+	if (data && !new_opts)
 		return -ENOMEM;

 	sync_filesystem(s);
@@ -466,7 +466,8 @@ static int hpfs_remount_fs(struct super_block *s, int *flags, char *data)

 	if (!(*flags & MS_RDONLY)) mark_dirty(s, 1);

-	replace_mount_options(s, new_opts);
+	if (new_opts)
+		replace_mount_options(s, new_opts);

 	hpfs_unlock(s);
 	return 0;
-- 
2.7.4