On Fri, Dec 22, 2017 at 03:32:26PM +0100, Dongsu Park wrote:
> From: Seth Forshee <seth.fors...@canonical.com>
>
> Unprivileged users should not be able to mount mtd block devices
> when they lack sufficient privileges towards the block device
> inode. Update mount_mtd() to validate that the user has the
> required access to the inode at the specified path. The check
> will be skipped for CAP_SYS_ADMIN, so privileged mounts will
> continue working as before.
>
> Patch v3 is available: https://patchwork.kernel.org/patch/7640011/
>
> Cc: linux-...@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Seth Forshee <seth.fors...@canonical.com>
> Signed-off-by: Dongsu Park <don...@kinvolk.io>
Acked-by: Serge Hallyn <se...@hallyn.com>
> ---
> drivers/mtd/mtdsuper.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c
> index 4a4d40c0..3c8734f3 100644
> --- a/drivers/mtd/mtdsuper.c
> +++ b/drivers/mtd/mtdsuper.c
> @@ -129,6 +129,7 @@ struct dentry *mount_mtd(struct file_system_type
> *fs_type, int flags,
> #ifdef CONFIG_BLOCK
> struct block_device *bdev;
> int ret, major;
> + int perm;
> #endif
> int mtdnr;
>
> @@ -180,7 +181,10 @@ struct dentry *mount_mtd(struct file_system_type
> *fs_type, int flags,
> /* try the old way - the hack where we allowed users to mount
> * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
> */
> - bdev = lookup_bdev(dev_name, 0);
> + perm = MAY_READ;
> + if (!(flags & MS_RDONLY))
> + perm |= MAY_WRITE;
> + bdev = lookup_bdev(dev_name, perm);
> if (IS_ERR(bdev)) {
> ret = PTR_ERR(bdev);
> pr_debug("MTDSB: lookup_bdev() returned %d\n", ret);
> --
> 2.13.6
>
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