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authorChristian Brauner <brauner@kernel.org>2023-01-13 12:49:27 +0100
committerChristian Brauner (Microsoft) <brauner@kernel.org>2023-01-19 09:24:29 +0100
commit9452e93e6dae862d7aeff2b11236d79bde6f9b66 (patch)
treebba173c3d83e596048a8c8fb34b373a0d315704e /fs/attr.c
parent01beba7957a26f9b7179127e8ad56bb5a0f56138 (diff)
fs: port privilege checking helpers to mnt_idmap
Convert to struct mnt_idmap. Last cycle we merged the necessary infrastructure in 256c8aed2b42 ("fs: introduce dedicated idmap type for mounts"). This is just the conversion to struct mnt_idmap. Currently we still pass around the plain namespace that was attached to a mount. This is in general pretty convenient but it makes it easy to conflate namespaces that are relevant on the filesystem with namespaces that are relevent on the mount level. Especially for non-vfs developers without detailed knowledge in this area this can be a potential source for bugs. Once the conversion to struct mnt_idmap is done all helpers down to the really low-level helpers will take a struct mnt_idmap argument instead of two namespace arguments. This way it becomes impossible to conflate the two eliminating the possibility of any bugs. All of the vfs and all filesystems only operate on struct mnt_idmap. Acked-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Diffstat (limited to 'fs/attr.c')
-rw-r--r--fs/attr.c53
1 files changed, 29 insertions, 24 deletions
diff --git a/fs/attr.c b/fs/attr.c
index bd8d542e13b9..2cadd055dbf2 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -23,7 +23,7 @@
/**
* setattr_should_drop_sgid - determine whether the setgid bit needs to be
* removed
- * @mnt_userns: user namespace of the mount @inode was found from
+ * @idmap: idmap of the mount @inode was found from
* @inode: inode to check
*
* This function determines whether the setgid bit needs to be removed.
@@ -33,16 +33,17 @@
*
* Return: ATTR_KILL_SGID if setgid bit needs to be removed, 0 otherwise.
*/
-int setattr_should_drop_sgid(struct user_namespace *mnt_userns,
+int setattr_should_drop_sgid(struct mnt_idmap *idmap,
const struct inode *inode)
{
+ struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
umode_t mode = inode->i_mode;
if (!(mode & S_ISGID))
return 0;
if (mode & S_IXGRP)
return ATTR_KILL_SGID;
- if (!in_group_or_capable(mnt_userns, inode,
+ if (!in_group_or_capable(idmap, inode,
i_gid_into_vfsgid(mnt_userns, inode)))
return ATTR_KILL_SGID;
return 0;
@@ -51,7 +52,7 @@ int setattr_should_drop_sgid(struct user_namespace *mnt_userns,
/**
* setattr_should_drop_suidgid - determine whether the set{g,u}id bit needs to
* be dropped
- * @mnt_userns: user namespace of the mount @inode was found from
+ * @idmap: idmap of the mount @inode was found from
* @inode: inode to check
*
* This function determines whether the set{g,u}id bits need to be removed.
@@ -63,7 +64,7 @@ int setattr_should_drop_sgid(struct user_namespace *mnt_userns,
* Return: A mask of ATTR_KILL_S{G,U}ID indicating which - if any - setid bits
* to remove, 0 otherwise.
*/
-int setattr_should_drop_suidgid(struct user_namespace *mnt_userns,
+int setattr_should_drop_suidgid(struct mnt_idmap *idmap,
struct inode *inode)
{
umode_t mode = inode->i_mode;
@@ -73,7 +74,7 @@ int setattr_should_drop_suidgid(struct user_namespace *mnt_userns,
if (unlikely(mode & S_ISUID))
kill = ATTR_KILL_SUID;
- kill |= setattr_should_drop_sgid(mnt_userns, inode);
+ kill |= setattr_should_drop_sgid(idmap, inode);
if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
return kill;
@@ -84,24 +85,26 @@ EXPORT_SYMBOL(setattr_should_drop_suidgid);
/**
* chown_ok - verify permissions to chown inode
- * @mnt_userns: user namespace of the mount @inode was found from
+ * @idmap: idmap of the mount @inode was found from
* @inode: inode to check permissions on
* @ia_vfsuid: uid to chown @inode to
*
- * If the inode has been found through an idmapped mount the user namespace of
- * the vfsmount must be passed through @mnt_userns. This function will then
- * take care to map the inode according to @mnt_userns before checking
+ * If the inode has been found through an idmapped mount the idmap of
+ * the vfsmount must be passed through @idmap. This function will then
+ * take care to map the inode according to @idmap before checking
* permissions. On non-idmapped mounts or if permission checking is to be
- * performed on the raw inode simply passs init_user_ns.
+ * performed on the raw inode simply pass @nop_mnt_idmap.
*/
-static bool chown_ok(struct user_namespace *mnt_userns,
+static bool chown_ok(struct mnt_idmap *idmap,
const struct inode *inode, vfsuid_t ia_vfsuid)
{
+ struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
+
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))
+ if (capable_wrt_inode_uidgid(idmap, inode, CAP_CHOWN))
return true;
if (!vfsuid_valid(vfsuid) &&
ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
@@ -111,19 +114,21 @@ static bool chown_ok(struct user_namespace *mnt_userns,
/**
* chgrp_ok - verify permissions to chgrp inode
- * @mnt_userns: user namespace of the mount @inode was found from
+ * @idmap: idmap of the mount @inode was found from
* @inode: inode to check permissions on
* @ia_vfsgid: gid to chown @inode to
*
- * If the inode has been found through an idmapped mount the user namespace of
- * the vfsmount must be passed through @mnt_userns. This function will then
- * take care to map the inode according to @mnt_userns before checking
+ * If the inode has been found through an idmapped mount the idmap of
+ * the vfsmount must be passed through @idmap. This function will then
+ * take care to map the inode according to @idmap before checking
* permissions. On non-idmapped mounts or if permission checking is to be
- * performed on the raw inode simply passs init_user_ns.
+ * performed on the raw inode simply pass @nop_mnt_idmap.
*/
-static bool chgrp_ok(struct user_namespace *mnt_userns,
+static bool chgrp_ok(struct mnt_idmap *idmap,
const struct inode *inode, vfsgid_t ia_vfsgid)
{
+ struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
+
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())) {
@@ -132,7 +137,7 @@ static bool chgrp_ok(struct user_namespace *mnt_userns,
if (vfsgid_in_group_p(ia_vfsgid))
return true;
}
- if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_CHOWN))
+ if (capable_wrt_inode_uidgid(idmap, inode, CAP_CHOWN))
return true;
if (!vfsgid_valid(vfsgid) &&
ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
@@ -184,12 +189,12 @@ int setattr_prepare(struct mnt_idmap *idmap, struct dentry *dentry,
/* Make sure a caller can chown. */
if ((ia_valid & ATTR_UID) &&
- !chown_ok(mnt_userns, inode, attr->ia_vfsuid))
+ !chown_ok(idmap, inode, attr->ia_vfsuid))
return -EPERM;
/* Make sure caller can chgrp. */
if ((ia_valid & ATTR_GID) &&
- !chgrp_ok(mnt_userns, inode, attr->ia_vfsgid))
+ !chgrp_ok(idmap, inode, attr->ia_vfsgid))
return -EPERM;
/* Make sure a caller can chmod. */
@@ -205,7 +210,7 @@ int setattr_prepare(struct mnt_idmap *idmap, struct dentry *dentry,
vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
/* Also check the setgid bit! */
- if (!in_group_or_capable(mnt_userns, inode, vfsgid))
+ if (!in_group_or_capable(idmap, inode, vfsgid))
attr->ia_mode &= ~S_ISGID;
}
@@ -316,7 +321,7 @@ void setattr_copy(struct mnt_idmap *idmap, struct inode *inode,
inode->i_ctime = attr->ia_ctime;
if (ia_valid & ATTR_MODE) {
umode_t mode = attr->ia_mode;
- if (!in_group_or_capable(mnt_userns, inode,
+ if (!in_group_or_capable(idmap, inode,
i_gid_into_vfsgid(mnt_userns, inode)))
mode &= ~S_ISGID;
inode->i_mode = mode;