From b27c82e1296572cfa3997e58db3118a33915f85c Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Tue, 21 Jun 2022 16:14:54 +0200 Subject: attr: port attribute changes to new types Now that we introduced new infrastructure to increase the type safety for filesystems supporting idmapped mounts port the first part of the vfs over to them. This ports the attribute changes codepaths to rely on the new better helpers using a dedicated type. Before this change we used to take a shortcut and place the actual values that would be written to inode->i_{g,u}id into struct iattr. This had the advantage that we moved idmappings mostly out of the picture early on but it made reasoning about changes more difficult than it should be. The filesystem was never explicitly told that it dealt with an idmapped mount. The transition to the value that needed to be stored in inode->i_{g,u}id appeared way too early and increased the probability of bugs in various codepaths. We know place the same value in struct iattr no matter if this is an idmapped mount or not. The vfs will only deal with type safe vfs{g,u}id_t. This makes it massively safer to perform permission checks as the type will tell us what checks we need to perform and what helpers we need to use. Fileystems raising FS_ALLOW_IDMAP can't simply write ia_vfs{g,u}id to inode->i_{g,u}id since they are different types. Instead they need to use the dedicated vfs{g,u}id_to_k{g,u}id() helpers that map the vfs{g,u}id into the filesystem. The other nice effect is that filesystems like overlayfs don't need to care about idmappings explicitly anymore and can simply set up struct iattr accordingly directly. Link: https://lore.kernel.org/lkml/CAHk-=win6+ahs1EwLkcq8apqLi_1wXFWbrPf340zYEhObpz4jA@mail.gmail.com [1] Link: https://lore.kernel.org/r/20220621141454.2914719-9-brauner@kernel.org Cc: Seth Forshee Cc: Christoph Hellwig Cc: Aleksa Sarai Cc: Linus Torvalds Cc: Al Viro CC: linux-fsdevel@vger.kernel.org Reviewed-by: Seth Forshee Signed-off-by: Christian Brauner (Microsoft) --- fs/quota/dquot.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'fs/quota') diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c index df9af1ce2851..28966da7834e 100644 --- a/fs/quota/dquot.c +++ b/fs/quota/dquot.c @@ -2096,8 +2096,11 @@ int dquot_transfer(struct user_namespace *mnt_userns, struct inode *inode, if (!dquot_active(inode)) return 0; - if (i_uid_needs_update(&init_user_ns, iattr, inode)) { - dquot = dqget(sb, make_kqid_uid(iattr->ia_uid)); + if (i_uid_needs_update(mnt_userns, iattr, inode)) { + kuid_t kuid = from_vfsuid(mnt_userns, i_user_ns(inode), + iattr->ia_vfsuid); + + dquot = dqget(sb, make_kqid_uid(kuid)); if (IS_ERR(dquot)) { if (PTR_ERR(dquot) != -ESRCH) { ret = PTR_ERR(dquot); @@ -2107,8 +2110,11 @@ int dquot_transfer(struct user_namespace *mnt_userns, struct inode *inode, } transfer_to[USRQUOTA] = dquot; } - if (i_gid_needs_update(&init_user_ns, iattr, inode)) { - dquot = dqget(sb, make_kqid_gid(iattr->ia_gid)); + if (i_gid_needs_update(mnt_userns, iattr, inode)) { + kgid_t kgid = from_vfsgid(mnt_userns, i_user_ns(inode), + iattr->ia_vfsgid); + + dquot = dqget(sb, make_kqid_gid(kgid)); if (IS_ERR(dquot)) { if (PTR_ERR(dquot) != -ESRCH) { ret = PTR_ERR(dquot); -- cgit v1.2.3-58-ga151