linux-kernel - [PATCHv2] fs: Don't return 0 from get_anon

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Date:	Thu,  3 Apr 2014 21:55:37 +0200
From:	Thomas Bächler <thomas@...hlinux.org>
To:	tj@...nel.org
Cc:	d@...conindy.com, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, P@...igbrady.com,
	alexandre.f.demers@...il.com,
	Thomas Bächler <thomas@...hlinux.org>,
	"3.14" <stable@...r.kernel.org>
Subject: [PATCHv2] fs: Don't return 0 from get_anon_bdev

Commit 9e30cc9595303b27b48 removed an internal mount. This
has the side-effect that rootfs now has FSID 0. Many
userspace utilities assume that st_dev in struct stat
is never 0, so this change breaks a number of tools in
early userspace.

Since we don't know how many userspace programs are affected,
make sure that FSID is at least 1.

References: http://article.gmane.org/gmane.linux.kernel/1666905
References: http://permalink.gmane.org/gmane.linux.utilities.util-linux-ng/8557
Cc: 3.14 <stable@...r.kernel.org>
Signed-off-by: Thomas Bächler <thomas@...hlinux.org>
---
 fs/super.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/super.c b/fs/super.c
index 80d5cf2..7624267 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -802,7 +802,10 @@ void emergency_remount(void)
 
 static DEFINE_IDA(unnamed_dev_ida);
 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
-static int unnamed_dev_start = 0; /* don't bother trying below it */
+/* Many userspace utilities consider an FSID of 0 invalid.
+ * Always return at least 1 from get_anon_bdev.
+ */
+static int unnamed_dev_start = 1;
 
 int get_anon_bdev(dev_t *p)
 {
-- 
1.9.1

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