[4.2.y-ckt stable] Patch "affs: 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

    affs: 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 10619f5f6aacbefc934e4c992081bce5d54bd4f7 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mikulas at twibright.com>
Date: Tue, 24 May 2016 22:48:33 +0200
Subject: affs: fix remount failure when there are no options changed

commit 01d6e08711bf90bc4d7ead14a93a0cbd73b1896a upstream.

Commit c8f33d0bec99 ("affs: kstrdup() 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: c8f33d0bec99 ("affs: kstrdup() 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/affs/super.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/affs/super.c b/fs/affs/super.c
index 3f89c9e..cc75712 100644
--- a/fs/affs/super.c
+++ b/fs/affs/super.c
@@ -526,7 +526,7 @@ affs_remount(struct super_block *sb, int *flags, char *data)
 	char			*prefix = NULL;

 	new_opts = kstrdup(data, GFP_KERNEL);
-	if (!new_opts)
+	if (data && !new_opts)
 		return -ENOMEM;

 	pr_debug("%s(flags=0x%x,opts=\"%s\")\n", __func__, *flags, data);
@@ -544,7 +544,8 @@ affs_remount(struct super_block *sb, int *flags, char *data)
 	}

 	flush_delayed_work(&sbi->sb_work);
-	replace_mount_options(sb, new_opts);
+	if (new_opts)
+		replace_mount_options(sb, new_opts);

 	sbi->s_flags = mount_flags;
 	sbi->s_mode  = mode;
--
2.7.4