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Re: [PATCH] xfs: Fix wrong error codes being returned

To: Tuomas Tynkkynen <tuomas.tynkkynen@xxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfs: Fix wrong error codes being returned
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Mon, 21 Apr 2014 20:46:39 +0800
Cc: linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1398074687-26548-1-git-send-email-tuomas.tynkkynen@xxxxxx>
References: <1398074687-26548-1-git-send-email-tuomas.tynkkynen@xxxxxx>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0
Hi Tuomas,

On 04/21 2014 18:04 PM, Tuomas Tynkkynen wrote:
> xfs_{compat_,}attrmulti_by_handle could return an errno with incorrect
> sign in some cases. While at it, make sure ENOMEM is returned instead of
> E2BIG if kmalloc fails.
> 
> Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@xxxxxx>
> ---
> Compile tested only. For the ERANGE case, I also wonder if it should
> be assigning to ops[i].am_error instead of error, and/or have a break.

If I understand right, ops[i].am_error is used to save the internal operation 
result,
i.e, xfs_attrmult_attr_get{set}... but error is used for the ioctl call results.
Therefore, assign ERANGE to error is compatible with the VFS set{get}xattr 
syscalls in
case of "if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)".

It seems that we don't need to have a break in this case because 
xfs_attrmulti_by_handle()
is used to process multiple attrs.  Hence if a given attrname in ops array is 
invalid,
the am_error will indicate that with ENOATTR or EFAULT...but it should proceed 
to loop
through the left array members.

Also, looks there is another minor issue at xfs_attrmulti_attr_set(), we should 
return
-PTR_ERR(kbuf) if call memdup_user() failed.

> 
>  fs/xfs/xfs_ioctl.c   |    5 +++--
>  fs/xfs/xfs_ioctl32.c |    5 +++--
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 0b18776..2d8f4fd 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -543,10 +543,11 @@ xfs_attrmulti_by_handle(
>  
>       ops = memdup_user(am_hreq.ops, size);
>       if (IS_ERR(ops)) {
> -             error = PTR_ERR(ops);
> +             error = -PTR_ERR(ops);
>               goto out_dput;
>       }
>  
> +     error = ENOMEM;
>       attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
>       if (!attr_name)
>               goto out_kfree_ops;
> @@ -556,7 +557,7 @@ xfs_attrmulti_by_handle(
>               ops[i].am_error = strncpy_from_user((char *)attr_name,
>                               ops[i].am_attrname, MAXNAMELEN);
>               if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
> -                     error = -ERANGE;
> +                     error = ERANGE;
>               if (ops[i].am_error < 0)
>                       break;
>  
> diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> index a7992f8..944d5ba 100644
> --- a/fs/xfs/xfs_ioctl32.c
> +++ b/fs/xfs/xfs_ioctl32.c
> @@ -424,10 +424,11 @@ xfs_compat_attrmulti_by_handle(
>  
>       ops = memdup_user(compat_ptr(am_hreq.ops), size);
>       if (IS_ERR(ops)) {
> -             error = PTR_ERR(ops);
> +             error = -PTR_ERR(ops);
>               goto out_dput;
>       }
>  
> +     error = ENOMEM;
>       attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
>       if (!attr_name)
>               goto out_kfree_ops;
> @@ -438,7 +439,7 @@ xfs_compat_attrmulti_by_handle(
>                               compat_ptr(ops[i].am_attrname),
>                               MAXNAMELEN);
>               if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
> -                     error = -ERANGE;
> +                     error = ERANGE;
>               if (ops[i].am_error < 0)
>                       break;
>  

Thanks,
-Jeff

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