Re: [PATCH 01/11] block_dev: Support checking inode permissions in lookup_bdev()
From: Coly Li <hidden>
Date: 2017-12-22 19:00:24
Also in:
dm-devel, linux-fsdevel, lkml
On 22/12/2017 10:32 PM, Dongsu Park wrote:
From: Seth Forshee <redacted> When looking up a block device by path no permission check is done to verify that the user has access to the block device inode at the specified path. In some cases it may be necessary to check permissions towards the inode, such as allowing unprivileged users to mount block devices in user namespaces. Add an argument to lookup_bdev() to optionally perform this permission check. A value of 0 skips the permission check and behaves the same as before. A non-zero value specifies the mask of access rights required towards the inode at the specified path. The check is always skipped if the user has CAP_SYS_ADMIN. All callers of lookup_bdev() currently pass a mask of 0, so this patch results in no functional change. Subsequent patches will add permission checks where appropriate. Patch v4 is available: https://patchwork.kernel.org/patch/8943601/ Cc: dm-devel@redhat.com Cc: linux-bcache@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-mtd@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jan Kara <jack@suse.com> Cc: Serge Hallyn <serge@hallyn.com> Signed-off-by: Seth Forshee <redacted> Signed-off-by: Dongsu Park <redacted>
Hi Dongsu, Could you please use a macro like NO_PERMISSION_CHECK to replace hard coded 0 ? At least for me, I don't need to check what does 0 mean in the new lookup_bdev(). Thanks. Coly Li
quoted hunk ↗ jump to hunk
--- drivers/md/bcache/super.c | 2 +- drivers/md/dm-table.c | 2 +- drivers/mtd/mtdsuper.c | 2 +- fs/block_dev.c | 13 ++++++++++--- fs/quota/quota.c | 2 +- include/linux/fs.h | 2 +- 6 files changed, 15 insertions(+), 8 deletions(-)diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index b4d28928..acc9d56c 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c@@ -1967,7 +1967,7 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr, sb); if (IS_ERR(bdev)) { if (bdev == ERR_PTR(-EBUSY)) { - bdev = lookup_bdev(strim(path)); + bdev = lookup_bdev(strim(path), 0); mutex_lock(&bch_register_lock); if (!IS_ERR(bdev) && bch_is_open(bdev)) err = "device already registered";diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 88130b5d..bca5eaf4 100644
[snip] -- Coly Li