[PATCH] fs: Don't return 0 from get_anon_bdev

[PATCH] fs: Don't return 0 from get_anon_bdev

[Thomas Bächler]

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@vger.kernel.org>
Signed-off-by: Thomas Bächler <thomas@archlinux.org>
---
 fs/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/super.c b/fs/super.c
index 80d5cf2..d9fddde 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -802,7 +802,7 @@ 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 */
+static int unnamed_dev_start = 1; /* don't bother trying below it */
 
 int get_anon_bdev(dev_t *p)
 {
-- 
1.9.1

Re: [PATCH] fs: Don't return 0 from get_anon_bdev

[Tejun Heo]

On Thu, Apr 03, 2014 at 09:49:55PM +0200, Thomas B�chler wrote:
> 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@vger.kernel.org>
> Signed-off-by: Thomas B�chler <thomas@archlinux.org>

Provided Alexandre confirms the fix.

 Acked-by: Tejun Heo <tj@kernel.org>

> ---
>  fs/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/super.c b/fs/super.c
> index 80d5cf2..d9fddde 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -802,7 +802,7 @@ 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 */
> +static int unnamed_dev_start = 1; /* don't bother trying below it */

Maybe a comment saying that userland considers fsid 0 to be invalid
would be nice?

Thanks.

-- 
tejun

[PATCHv2] fs: Don't return 0 from get_anon_bdev

[Thomas Bächler]

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@vger.kernel.org>
Signed-off-by: Thomas Bächler <thomas@archlinux.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

Re: [PATCH] fs: Don't return 0 from get_anon_bdev

[H. Peter Anvin]

On 04/03/2014 12:49 PM, Thomas Bächler wrote:
> 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@vger.kernel.org>
> Signed-off-by: Thomas Bächler <thomas@archlinux.org>
> ---
>  fs/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 

Acked-by: H. Peter Anvin <hpa@zytor.com>

It is worth noting that zero has been documented as a null device number
since at least 1995, probably more like 1993.

	-hpa

Re: [PATCHv2] fs: Don't return 0 from get_anon_bdev

[Greg KH]

On Thu, Apr 03, 2014 at 09:55:37PM +0200, Thomas B�chler wrote:
> 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@vger.kernel.org>
> Signed-off-by: Thomas B�chler <thomas@archlinux.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)
>  {

Very nice, I'll go queue this one up instead of the other patch from
Tejun.

greg k-h

Re: [PATCH] fs: Don't return 0 from get_anon_bdev

[Alexandre Demers]

It works over here, tested on 3.14-rc8 which was previously failing. You 
have my

Tested-by: Alexandre Demers

Alexandre Demers

On 04/03/2014 03:49 PM, Thomas Bächler wrote:
> 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@vger.kernel.org>
> Signed-off-by: Thomas Bächler <thomas@archlinux.org>
> ---
>   fs/super.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/super.c b/fs/super.c
> index 80d5cf2..d9fddde 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -802,7 +802,7 @@ 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 */
> +static int unnamed_dev_start = 1; /* don't bother trying below it */
>   
>   int get_anon_bdev(dev_t *p)
>   {