linux-kernel - Re: [PATCH] Make __xfs_xattr_put

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Message-ID: <20160824015551.GB19025@dastard>
Date:   Wed, 24 Aug 2016 11:55:51 +1000
From:   Dave Chinner <david@...morbit.com>
To:     Artem Savkov <asavkov@...hat.com>
Cc:     Eric Sandeen <sandeen@...deen.net>, xfs@....sgi.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Make __xfs_xattr_put_listen preperly report errors.

On Tue, Aug 23, 2016 at 05:54:13PM +0200, Artem Savkov wrote:
> Commit "xfs: only return -errno or success from attr ->put_listent" changes the

Please quote commits in --oneline format in changelogs - it makes it
much easier to find the change you are refering to if there is both
a commit ID and the text string in the commit message. (i.e. text
string confirms the commit id is the one you meant to quote).

commit 2a6fba6 ("xfs: only return -errno or success from attr
->put_listent") is the one you are refering to here, right?

> returnvalue of __xfs_xattr_put_listen to 0 in case when there is insufficient
> space in the buffer assuming that setting context->count to -1 would be enough,
> but all of the ->put_listent callers only check seen_enough. This results in
> a failed assertion:
> XFS: Assertion failed: context->count >= 0, file: fs/xfs/xfs_xattr.c, line: 175
> in insufficient buffer size case.

You have a test case? Can you turn it into an xfstest? We really
need regression tests that cover issues like this....

> Signed-off-by: Artem Savkov <asavkov@...hat.com>
> ---
>  fs/xfs/xfs_xattr.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
> index ea62245..6290093 100644
> --- a/fs/xfs/xfs_xattr.c
> +++ b/fs/xfs/xfs_xattr.c
> @@ -147,6 +147,7 @@ __xfs_xattr_put_listent(
>  	arraytop = context->count + prefix_len + namelen + 1;
>  	if (arraytop > context->firstu) {
>  		context->count = -1;	/* insufficient space */
> +		context->seen_enough = 1;
>  		return 0;
>  	}
>  	offset = (char *)context->alist + context->count;

Looks sane, though I don't know how to test it yet....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com