[bug report] UBI: Fastmap: Do not add vol if it already exists

[Boris Brezillon]

+ Richard

On Wed, 26 Oct 2016 11:25:36 +0300
Dan Carpenter <dan.carpenter at oracle.com> wrote:

> On Wed, Oct 26, 2016 at 09:46:51AM +0800, Sheng Yong wrote:
> > Hi Dan,
> > 
> > On 10/26/2016 4:46 AM, Dan Carpenter wrote:  
> > > Hello shengyong,
> > > 
> > > The patch e96a8a3bb671: "UBI: Fastmap: Do not add vol if it already
> > > exists" from May 26, 2015, leads to the following static checker
> > > warning:
> > > 
> > > 	drivers/mtd/ubi/fastmap.c:712 ubi_attach_fastmap()
> > > 	warn: PTR_ERR(av) is never (-22)
> > > 
> > > drivers/mtd/ubi/fastmap.c
> > >    703  
> > >    704                  av = add_vol(ai, be32_to_cpu(fmvhdr->vol_id),
> > >    705                               be32_to_cpu(fmvhdr->used_ebs),
> > >    706                               be32_to_cpu(fmvhdr->data_pad),
> > >    707                               fmvhdr->vol_type,
> > >    708                               be32_to_cpu(fmvhdr->last_eb_bytes));
> > >    709  
> > >    710                  if (!av)
> > >    711                          goto fail_bad;
> > >    712                  if (PTR_ERR(av) == -EINVAL) {
> > > 
> > > av is either -EEXIST or -ENOMEM.  It's never -EINVAL.  
> > The commit e96a8a3bb671 ("UBI: Fastmap: Do not add vol if it already exists")
> > adds a "return ERR_PTR(-EINVAL);" to add_vol(). So I think av could be -EINVAL.
> > You mean add_vol should return -EEXIST instead of -EINVAL?
> >  
> 
> Oh, ah.  I'm on linux-next.  Commit de4c455b3e9f ("UBI: factorize code
> used to manipulate volumes at attach time") removed the -EINVAL.
> 
> It's really Boris to blame for this warning.  I'm not sure what the fix
> is.

Yes, sorry, I didn't notice the caller was explicitly testing for
-EINVAL.

Here is a patch fixing the problem:

--->8---
From 66d46bb212a8fcdcdd54def051492abb1668f1b2 Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon at free-electrons.com>
Date: Wed, 26 Oct 2016 11:17:03 +0200
Subject: [PATCH] UBI: fastmap: Fix add_vol() return value test in
 ubi_attach_fastmap()

Commit e96a8a3bb671 ("UBI: Fastmap: Do not add vol if it already
exists") introduced a bug by changing the possible error codes returned
by add_vol():
- this functions no longer returns NULL in case of allocation failure
  but return ERR_PTR(-ENOMEM)
- when a duplicate entry in the volume RB tree is found it returns
  ERR_PTR(-EEXIST) instead of ERR_PTR(-EINVAL)

Fix the tests done of add_vol() return value accordingly.

Fixes: e96a8a3bb671 ("UBI: Fastmap: Do not add vol if it already exists")
Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
---
 drivers/mtd/ubi/fastmap.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/ubi/fastmap.c b/drivers/mtd/ubi/fastmap.c
index d6384d965788..eb39c44726e3 100644
--- a/drivers/mtd/ubi/fastmap.c
+++ b/drivers/mtd/ubi/fastmap.c
@@ -707,11 +707,11 @@ static int ubi_attach_fastmap(struct ubi_device *ubi,
 			     fmvhdr->vol_type,
 			     be32_to_cpu(fmvhdr->last_eb_bytes));
 
-		if (!av)
-			goto fail_bad;
-		if (PTR_ERR(av) == -EINVAL) {
-			ubi_err(ubi, "volume (ID %i) already exists",
-				fmvhdr->vol_id);
+		if (IS_ERR(av)) {
+			if (PTR_ERR(av) == -EEXIST)
+				ubi_err(ubi, "volume (ID %i) already exists",
+					fmvhdr->vol_id);
+
 			goto fail_bad;
 		}