From 47291baa8ddfdae10663624ff0a15ab165952708 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:24 +0100 Subject: namei: make permission helpers idmapped mount aware The two helpers inode_permission() and generic_permission() are used by the vfs to perform basic permission checking by verifying that the caller is privileged over an inode. In order to handle idmapped mounts we extend the two helpers with an additional user namespace argument. On idmapped mounts the two helpers will make sure to map the inode according to the mount's user namespace and then peform identical permission checks to inode_permission() and generic_permission(). If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-6-christian.brauner@ubuntu.com Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Reviewed-by: James Morris Acked-by: Serge Hallyn Signed-off-by: Christian Brauner --- fs/kernfs/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/kernfs/inode.c') diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index fc2469a20fed..ff5598cc1de0 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -285,7 +285,7 @@ int kernfs_iop_permission(struct inode *inode, int mask) kernfs_refresh_inode(kn, inode); mutex_unlock(&kernfs_mutex); - return generic_permission(inode, mask); + return generic_permission(&init_user_ns, inode, mask); } int kernfs_xattr_get(struct kernfs_node *kn, const char *name, -- cgit v1.2.3 From 2f221d6f7b881d95de1f356a3097d755ab1e47d4 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:26 +0100 Subject: attr: handle idmapped mounts When file attributes are changed most filesystems rely on the setattr_prepare(), setattr_copy(), and notify_change() helpers for initialization and permission checking. Let them handle idmapped mounts. If the inode is accessed through an idmapped mount map it into the mount's user namespace. Afterwards the checks are identical to non-idmapped mounts. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Helpers that perform checks on the ia_uid and ia_gid fields in struct iattr assume that ia_uid and ia_gid are intended values and have already been mapped correctly at the userspace-kernelspace boundary as we already do today. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-8-christian.brauner@ubuntu.com Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner --- fs/kernfs/inode.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/kernfs/inode.c') diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index ff5598cc1de0..86bd4c593b78 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -122,7 +122,7 @@ int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr) return -EINVAL; mutex_lock(&kernfs_mutex); - error = setattr_prepare(dentry, iattr); + error = setattr_prepare(&init_user_ns, dentry, iattr); if (error) goto out; @@ -131,7 +131,7 @@ int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr) goto out; /* this ignores size changes */ - setattr_copy(inode, iattr); + setattr_copy(&init_user_ns, inode, iattr); out: mutex_unlock(&kernfs_mutex); -- cgit v1.2.3 From e65ce2a50cf6af216bea6fd80d771fcbb4c0aaa1 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:27 +0100 Subject: acl: handle idmapped mounts The posix acl permission checking helpers determine whether a caller is privileged over an inode according to the acls associated with the inode. Add helpers that make it possible to handle acls on idmapped mounts. The vfs and the filesystems targeted by this first iteration make use of posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to translate basic posix access and default permissions such as the ACL_USER and ACL_GROUP type according to the initial user namespace (or the superblock's user namespace) to and from the caller's current user namespace. Adapt these two helpers to handle idmapped mounts whereby we either map from or into the mount's user namespace depending on in which direction we're translating. Similarly, cap_convert_nscap() is used by the vfs to translate user namespace and non-user namespace aware filesystem capabilities from the superblock's user namespace to the caller's user namespace. Enable it to handle idmapped mounts by accounting for the mount's user namespace. In addition the fileystems targeted in the first iteration of this patch series make use of the posix_acl_chmod() and, posix_acl_update_mode() helpers. Both helpers perform permission checks on the target inode. Let them handle idmapped mounts. These two helpers are called when posix acls are set by the respective filesystems to handle this case we extend the ->set() method to take an additional user namespace argument to pass the mount's user namespace down. Link: https://lore.kernel.org/r/20210121131959.646623-9-christian.brauner@ubuntu.com Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner --- fs/kernfs/inode.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'fs/kernfs/inode.c') diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index 86bd4c593b78..7e44052b42e1 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -319,6 +319,7 @@ static int kernfs_vfs_xattr_get(const struct xattr_handler *handler, } static int kernfs_vfs_xattr_set(const struct xattr_handler *handler, + struct user_namespace *mnt_userns, struct dentry *unused, struct inode *inode, const char *suffix, const void *value, size_t size, int flags) @@ -385,6 +386,7 @@ static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn, } static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler, + struct user_namespace *mnt_userns, struct dentry *unused, struct inode *inode, const char *suffix, const void *value, size_t size, int flags) -- cgit v1.2.3 From 0d56a4518d5eaf595a24ab2202e171330bb2ed72 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:30 +0100 Subject: stat: handle idmapped mounts The generic_fillattr() helper fills in the basic attributes associated with an inode. Enable it to handle idmapped mounts. If the inode is accessed through an idmapped mount map it into the mount's user namespace before we store the uid and gid. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210121131959.646623-12-christian.brauner@ubuntu.com Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Reviewed-by: James Morris Signed-off-by: Christian Brauner --- fs/kernfs/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/kernfs/inode.c') diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index 7e44052b42e1..032d3d7546d8 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -193,7 +193,7 @@ int kernfs_iop_getattr(const struct path *path, struct kstat *stat, kernfs_refresh_inode(kn, inode); mutex_unlock(&kernfs_mutex); - generic_fillattr(inode, stat); + generic_fillattr(&init_user_ns, inode, stat); return 0; } -- cgit v1.2.3 From 549c7297717c32ee53f156cd949e055e601f67bb Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:43 +0100 Subject: fs: make helpers idmap mount aware Extend some inode methods with an additional user namespace argument. A filesystem that is aware of idmapped mounts will receive the user namespace the mount has been marked with. This can be used for additional permission checking and also to enable filesystems to translate between uids and gids if they need to. We have implemented all relevant helpers in earlier patches. As requested we simply extend the exisiting inode method instead of introducing new ones. This is a little more code churn but it's mostly mechanical and doesnt't leave us with additional inode methods. Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner --- fs/kernfs/inode.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'fs/kernfs/inode.c') diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index 032d3d7546d8..d73950fc3d57 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -112,7 +112,8 @@ int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr) return ret; } -int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr) +int kernfs_iop_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, + struct iattr *iattr) { struct inode *inode = d_inode(dentry); struct kernfs_node *kn = inode->i_private; @@ -183,7 +184,8 @@ static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode) set_nlink(inode, kn->dir.subdirs + 2); } -int kernfs_iop_getattr(const struct path *path, struct kstat *stat, +int kernfs_iop_getattr(struct user_namespace *mnt_userns, + const struct path *path, struct kstat *stat, u32 request_mask, unsigned int query_flags) { struct inode *inode = d_inode(path->dentry); @@ -272,7 +274,8 @@ void kernfs_evict_inode(struct inode *inode) kernfs_put(kn); } -int kernfs_iop_permission(struct inode *inode, int mask) +int kernfs_iop_permission(struct user_namespace *mnt_userns, + struct inode *inode, int mask) { struct kernfs_node *kn; -- cgit v1.2.3