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Re: [PATCH] Fix possible memory corruption in xfs_readlink

To: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
Subject: Re: [PATCH] Fix possible memory corruption in xfs_readlink
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 18 Oct 2011 09:43:09 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <1318885528-7650-1-git-send-email-cmaiolino@xxxxxxxxxx>
References: <1318885528-7650-1-git-send-email-cmaiolino@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Oct 17, 2011 at 07:05:28PM -0200, Carlos Maiolino wrote:
> Fixes a possible memory corruption when the link is larger than
> MAXPATHLEN and XFS_DEBUG is not enabled. This also remove the
> S_ISLNK assert, since the inode mode is checked previously in
> xfs_readlink_by_handle() and via VFS.
> 
> Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>

Looks good. One minor thing for consistency, but consider it:

Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>

> ---
>  fs/xfs/xfs_vnodeops.c |   11 ++++++++---
>  1 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
> index 51fc429..9ca6676 100644
> --- a/fs/xfs/xfs_vnodeops.c
> +++ b/fs/xfs/xfs_vnodeops.c
> @@ -123,13 +123,18 @@ xfs_readlink(
>  
>       xfs_ilock(ip, XFS_ILOCK_SHARED);
>  
> -     ASSERT(S_ISLNK(ip->i_d.di_mode));
> -     ASSERT(ip->i_d.di_size <= MAXPATHLEN);
> -
>       pathlen = ip->i_d.di_size;
>       if (!pathlen)
>               goto out;
>  
> +     if (pathlen > MAXPATHLEN) {
> +             xfs_emerg(mp, "%s: inode (%lld) symlink length (%d) too long",
> +                      __func__, (unsigned long long)ip->i_ino, pathlen);

xfs_alert() is generally used for such messages - it's not a fatal
error (yet)....

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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