Re: [PATCH 02/19] block_dev: Check permissions towards block device inode when mounting

Serge E. Hallyn
2015-12-04T16:28:07Z

On Wed, Dec 02, 2015 at 09:40:02AM -0600, Seth Forshee wrote:
> Unprivileged users should not be able to mount block devices when
> they lack sufficient privileges towards the block device inode.
> Update blkdev_get_by_path() 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.
>
> Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>

> ---
> fs/block_dev.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 3ebbde85d898..4fdb6ab59816 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1424,9 +1424,14 @@ struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
> void *holder)
> {
> struct block_device *bdev;
> + int perm = 0;
> int err;
>
> - bdev = lookup_bdev(path, 0);
> + if (mode & FMODE_READ)
> + perm |= MAY_READ;
> + if (mode & FMODE_WRITE)
> + perm |= MAY_WRITE;
> + bdev = lookup_bdev(path, perm);
> if (IS_ERR(bdev))
> return bdev;
>
> --
> 1.9.1
>
> --
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