[4.2.y-ckt stable] Patch "hpfs: fix remount failure when there are no options changed" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    hpfs: fix remount failure when there are no options changed

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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

>From f911b6c9717fec70ee1eae1ee7b1cd11558e5ba3 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mikulas at twibright.com>
Date: Tue, 24 May 2016 22:47:00 +0200
Subject: hpfs: fix remount failure when there are no options changed

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 at redhat.com>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.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 68a9bed..8c2b6e9 100644
--- a/fs/hpfs/super.c
+++ b/fs/hpfs/super.c
@@ -455,7 +455,7 @@ 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);
@@ -493,7 +493,8 @@ 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