Jörg,

On 28.10.2016 18:19, Jörg Krause wrote:

Hi,

On Fri, 2016-10-28 at 11:53 +0200, Richard Weinberger wrote:

quoted

Commit c83ed4c9dbb35 ("ubifs: Abort readdir upon error") broke
overlayfs support because the fix exposed an internal error
code to VFS.

Reported-by: Peter Rosin <redacted>
Tested-by: Peter Rosin <redacted>
Reported-by: Ralph Sennhauser <redacted>
Fixes: c83ed4c9dbb35 ("ubifs: Abort readdir upon error")
Cc: stable@vger.kernel.org
Signed-off-by: Richard Weinberger <richard@nod.at>
---
 fs/ubifs/dir.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index bd4a5e8ce441..ca16c5d7bab1 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c

@@ -543,6 +543,14 @@ static int ubifs_readdir(struct file *file,

struct dir_context *ctx)
 
 	if (err != -ENOENT)
 		ubifs_err(c, "cannot find next direntry, error %d",
err);
+	else
+		/*
+		 * -ENOENT is a non-fatal error in this context, the
TNC uses
+		 * it to indicate that the cursor moved past the
current directory
+		 * and readdir() has to stop.
+		 */
+		err = 0;
+
 
 	/* 2 is a special value indicating that there are no more
direntries */
 	ctx->pos = 2;

I'm not sure if it's related to the issue reported by Peter Rosin and
Ralph Sennhauser, but I am still getting a kernel panic using UBIFS
with OverlayFS on Linux v4.9.0-rc2 with this patch applied:

Does reverting c83ed4c9dbb35 help?
And are you 100% sure you applied the fix?

Does the following WARN_ON() trigger?

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index ca16c5d7bab1..12ffc91f7ef8 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c

@@ -554,6 +554,9 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)

 	/* 2 is a special value indicating that there are no more direntries */
 	ctx->pos = 2;
+
+	WARN_ON(err);
+
 	return err;
 }

Thanks,
//richard