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Re: [PATCH V2] xfs: zero proper structure size for geometry calls

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: [PATCH V2] xfs: zero proper structure size for geometry calls
From: Dan Rosenberg <drosenberg@xxxxxxxxxxxxx>
Date: Tue, 01 Mar 2011 07:55:32 -0500
Cc: Jeffrey Hundstad <jeffrey.hundstad@xxxxxxxx>, Eugene Teo <eugeneteo@xxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <4D6C9958.2040607@xxxxxxxxxxx>
References: <4D6C28A5.60905@xxxxxxxx> <4D6C4DEE.6020902@xxxxxxxxxxx> <4D6C9958.2040607@xxxxxxxxxxx>
On Tue, 2011-03-01 at 00:59 -0600, Eric Sandeen wrote:
> commit 493f3358cb289ccf716c5a14fa5bb52ab75943e5 added:
> 
> +       memset(geo, 0, sizeof(*geo)); 
> 
> but unfortunately we're dealing with a cast pointer here, and
> the caller may actually have a smaller structure on the stack.
> Zeroing out more leads to stack corruption traps:
> 
> Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: 
> f87aca93
> 
> Pid: 262, comm: xfs_fsr Not tainted 2.6.38-rc6-493f3358cb2+ #1
> Call Trace:
> 
> [<c12991ac>] ? panic+0x50/0x150
> [<c102ed71>] ? __stack_chk_fail+0x10/0x18
> [<f87aca93>] ? xfs_ioc_fsgeometry_v1+0x56/0x5d [xfs] 
> 
> Fix this by zeroing out the structure in the callers, where we know
> the actual size.

Thanks for catching this early, and sorry for the misstep.

Reviewed-by: Dan Rosenberg <drosenberg@xxxxxxxxxxxxx>

> 
> Reported-by: Jeffrey Hundstad <jeffrey.hundstad@xxxxxxxx>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
> 
> V2: Use sizeof (variable) not sizeof (type)
> 
> diff --git a/fs/xfs/linux-2.6/xfs_ioctl.c b/fs/xfs/linux-2.6/xfs_ioctl.c
> index f5e2a19..871e5f0 100644
> --- a/fs/xfs/linux-2.6/xfs_ioctl.c
> +++ b/fs/xfs/linux-2.6/xfs_ioctl.c
> @@ -698,6 +698,7 @@ xfs_ioc_fsgeometry_v1(
>       xfs_fsop_geom_v1_t      fsgeo;
>       int                     error;
>  
> +     memset(&fsgeo, 0, sizeof(fsgeo));
>       error = xfs_fs_geometry(mp, (xfs_fsop_geom_t *)&fsgeo, 3);
>       if (error)
>               return -error;
> @@ -715,6 +716,7 @@ xfs_ioc_fsgeometry(
>       xfs_fsop_geom_t         fsgeo;
>       int                     error;
>  
> +     memset(&fsgeo, 0, sizeof(fsgeo));
>       error = xfs_fs_geometry(mp, &fsgeo, 4);
>       if (error)
>               return -error;
> diff --git a/fs/xfs/linux-2.6/xfs_ioctl32.c b/fs/xfs/linux-2.6/xfs_ioctl32.c
> index b3486df..f25d38e 100644
> --- a/fs/xfs/linux-2.6/xfs_ioctl32.c
> +++ b/fs/xfs/linux-2.6/xfs_ioctl32.c
> @@ -73,6 +73,7 @@ xfs_compat_ioc_fsgeometry_v1(
>       xfs_fsop_geom_t           fsgeo;
>       int                       error;
>  
> +     memset(&fsgeo, 0, sizeof(fsgeo));
>       error = xfs_fs_geometry(mp, &fsgeo, 3);
>       if (error)
>               return -error;
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index 85668ef..cec89dd 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -53,9 +53,6 @@ xfs_fs_geometry(
>       xfs_fsop_geom_t         *geo,
>       int                     new_version)
>  {
> -
> -     memset(geo, 0, sizeof(*geo));
> -
>       geo->blocksize = mp->m_sb.sb_blocksize;
>       geo->rtextsize = mp->m_sb.sb_rextsize;
>       geo->agblocks = mp->m_sb.sb_agblocks;


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