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authorChristian Brauner <brauner@kernel.org>2022-06-21 16:14:54 +0200
committerChristian Brauner (Microsoft) <brauner@kernel.org>2022-06-26 18:18:56 +0200
commitb27c82e1296572cfa3997e58db3118a33915f85c (patch)
treeff3c2f626affd196f54ee985da02c81343e4050c /fs/attr.c
parent0e363cf3fa598c69340794da068d4d9cbc869322 (diff)
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 <sforshee@digitalocean.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Aleksa Sarai <cyphar@cyphar.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> CC: linux-fsdevel@vger.kernel.org Reviewed-by: Seth Forshee <sforshee@digitalocean.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Diffstat (limited to 'fs/attr.c')
-rw-r--r--fs/attr.c68
1 files changed, 32 insertions, 36 deletions
diff --git a/fs/attr.c b/fs/attr.c
index 88e2ca30d42e..1ba7ddef537f 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -31,15 +31,15 @@
* performed on the raw inode simply passs init_user_ns.
*/
static bool chown_ok(struct user_namespace *mnt_userns,
- const struct inode *inode,
- kuid_t uid)
+ const struct inode *inode, vfsuid_t ia_vfsuid)
{
- kuid_t kuid = i_uid_into_mnt(mnt_userns, inode);
- if (uid_eq(current_fsuid(), kuid) && uid_eq(uid, inode->i_uid))
+ vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
+ if (vfsuid_eq_kuid(vfsuid, current_fsuid()) &&
+ vfsuid_eq(ia_vfsuid, vfsuid))
return true;
if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_CHOWN))
return true;
- if (uid_eq(kuid, INVALID_UID) &&
+ if (!vfsuid_valid(vfsuid) &&
ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
return true;
return false;
@@ -58,21 +58,19 @@ static bool chown_ok(struct user_namespace *mnt_userns,
* performed on the raw inode simply passs init_user_ns.
*/
static bool chgrp_ok(struct user_namespace *mnt_userns,
- const struct inode *inode, kgid_t gid)
+ const struct inode *inode, vfsgid_t ia_vfsgid)
{
- kgid_t kgid = i_gid_into_mnt(mnt_userns, inode);
- if (uid_eq(current_fsuid(), i_uid_into_mnt(mnt_userns, inode))) {
- kgid_t mapped_gid;
-
- if (gid_eq(gid, inode->i_gid))
+ vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
+ vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
+ if (vfsuid_eq_kuid(vfsuid, current_fsuid())) {
+ if (vfsgid_eq(ia_vfsgid, vfsgid))
return true;
- mapped_gid = mapped_kgid_fs(mnt_userns, i_user_ns(inode), gid);
- if (in_group_p(mapped_gid))
+ if (vfsgid_in_group_p(ia_vfsgid))
return true;
}
if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_CHOWN))
return true;
- if (gid_eq(kgid, INVALID_GID) &&
+ if (!vfsgid_valid(vfsgid) &&
ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
return true;
return false;
@@ -120,28 +118,29 @@ int setattr_prepare(struct user_namespace *mnt_userns, struct dentry *dentry,
goto kill_priv;
/* Make sure a caller can chown. */
- if ((ia_valid & ATTR_UID) && !chown_ok(mnt_userns, inode, attr->ia_uid))
+ if ((ia_valid & ATTR_UID) &&
+ !chown_ok(mnt_userns, inode, attr->ia_vfsuid))
return -EPERM;
/* Make sure caller can chgrp. */
- if ((ia_valid & ATTR_GID) && !chgrp_ok(mnt_userns, inode, attr->ia_gid))
+ if ((ia_valid & ATTR_GID) &&
+ !chgrp_ok(mnt_userns, inode, attr->ia_vfsgid))
return -EPERM;
/* Make sure a caller can chmod. */
if (ia_valid & ATTR_MODE) {
- kgid_t mapped_gid;
+ vfsgid_t vfsgid;
if (!inode_owner_or_capable(mnt_userns, inode))
return -EPERM;
if (ia_valid & ATTR_GID)
- mapped_gid = mapped_kgid_fs(mnt_userns,
- i_user_ns(inode), attr->ia_gid);
+ vfsgid = attr->ia_vfsgid;
else
- mapped_gid = i_gid_into_mnt(mnt_userns, inode);
+ vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
/* Also check the setgid bit! */
- if (!in_group_p(mapped_gid) &&
+ if (!vfsgid_in_group_p(vfsgid) &&
!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
attr->ia_mode &= ~S_ISGID;
}
@@ -219,9 +218,7 @@ EXPORT_SYMBOL(inode_newsize_ok);
* setattr_copy must be called with i_mutex held.
*
* setattr_copy updates the inode's metadata with that specified
- * in attr on idmapped mounts. If file ownership is changed setattr_copy
- * doesn't map ia_uid and ia_gid. It will asssume the caller has already
- * provided the intended values. Necessary permission checks to determine
+ * in attr on idmapped mounts. Necessary permission checks to determine
* whether or not the S_ISGID property needs to be removed are performed with
* the correct idmapped mount permission helpers.
* Noticeably missing is inode size update, which is more complex
@@ -242,8 +239,8 @@ void setattr_copy(struct user_namespace *mnt_userns, struct inode *inode,
{
unsigned int ia_valid = attr->ia_valid;
- i_uid_update(&init_user_ns, attr, inode);
- i_gid_update(&init_user_ns, attr, inode);
+ i_uid_update(mnt_userns, attr, inode);
+ i_gid_update(mnt_userns, attr, inode);
if (ia_valid & ATTR_ATIME)
inode->i_atime = attr->ia_atime;
if (ia_valid & ATTR_MTIME)
@@ -252,8 +249,8 @@ void setattr_copy(struct user_namespace *mnt_userns, struct inode *inode,
inode->i_ctime = attr->ia_ctime;
if (ia_valid & ATTR_MODE) {
umode_t mode = attr->ia_mode;
- kgid_t kgid = i_gid_into_mnt(mnt_userns, inode);
- if (!in_group_p(kgid) &&
+ vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
+ if (!vfsgid_in_group_p(vfsgid) &&
!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
mode &= ~S_ISGID;
inode->i_mode = mode;
@@ -304,9 +301,6 @@ EXPORT_SYMBOL(may_setattr);
* retry. Because breaking a delegation may take a long time, the
* caller should drop the i_mutex before doing so.
*
- * If file ownership is changed notify_change() doesn't map ia_uid and
- * ia_gid. It will asssume the caller has already provided the intended values.
- *
* Alternatively, a caller may pass NULL for delegated_inode. This may
* be appropriate for callers that expect the underlying filesystem not
* to be NFS exported. Also, passing NULL is fine for callers holding
@@ -395,23 +389,25 @@ int notify_change(struct user_namespace *mnt_userns, struct dentry *dentry,
* namespace of the superblock.
*/
if (ia_valid & ATTR_UID &&
- !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
+ !vfsuid_has_fsmapping(mnt_userns, inode->i_sb->s_user_ns,
+ attr->ia_vfsuid))
return -EOVERFLOW;
if (ia_valid & ATTR_GID &&
- !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
+ !vfsgid_has_fsmapping(mnt_userns, inode->i_sb->s_user_ns,
+ attr->ia_vfsgid))
return -EOVERFLOW;
/* Don't allow modifications of files with invalid uids or
* gids unless those uids & gids are being made valid.
*/
if (!(ia_valid & ATTR_UID) &&
- !uid_valid(i_uid_into_mnt(mnt_userns, inode)))
+ !vfsuid_valid(i_uid_into_vfsuid(mnt_userns, inode)))
return -EOVERFLOW;
if (!(ia_valid & ATTR_GID) &&
- !gid_valid(i_gid_into_mnt(mnt_userns, inode)))
+ !vfsgid_valid(i_gid_into_vfsgid(mnt_userns, inode)))
return -EOVERFLOW;
- error = security_inode_setattr(&init_user_ns, dentry, attr);
+ error = security_inode_setattr(mnt_userns, dentry, attr);
if (error)
return error;
error = try_break_deleg(inode, delegated_inode);