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> --- 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
