linux-kernel - Re: [2.6.33 regression] btrfs mount causes memory corruption

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Date:	Thu, 25 Feb 2010 15:48:21 -0500
From:	Andrew Lutomirski <luto@....edu>
To:	Josef Bacik <josef@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org
Subject: Re: [2.6.33 regression] btrfs mount causes memory corruption

On Thu, Feb 25, 2010 at 3:38 PM, Josef Bacik <josef@...hat.com> wrote:
>
> Ok it looks like we have a problem kfree'ing the wrong stuff.  we kstrdup the
> options string, but then strsep screws with the pointer, so when we kfree() it,
> we're not giving it the right pointer.  Please try this patch, and mount with -o
> acl and other such garbage to make sure it actually worked (acl isn't a valid
> mount option btw).  Let me know if it works.  Thanks,
>
> Josef
>
>
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 8a1ea6e..f8b4521 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -128,7 +128,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
>  {
>        struct btrfs_fs_info *info = root->fs_info;
>        substring_t args[MAX_OPT_ARGS];
> -       char *p, *num;
> +       char *p, *num, *orig;
>        int intarg;
>        int ret = 0;
>
> @@ -143,6 +143,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
>        if (!options)
>                return -ENOMEM;
>
> +       orig = options;
>
>        while ((p = strsep(&options, ",")) != NULL) {
>                int token;
> @@ -280,7 +281,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
>                }
>        }
>  out:
> -       kfree(options);
> +       kfree(orig);
>        return ret;
>  }
>
>


Thanks for the instant patch.  I hammered on it a bit and it hasn't
crashed yet.  I'll let you know if it crashes later.  (The earlier
trial with xattr crashed after a couple minutes.)

In the mean time,

Tested-by: Andy Lutomirski <luto@....edu>

--Andy
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