From 02f92b3868a1b34ab98464e76b0e4e060474ba10 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:22 +0100 Subject: fs: add file and path permissions helpers Add two simple helpers to check permissions on a file and path respectively and convert over some callers. It simplifies quite a few codepaths and also reduces the churn in later patches quite a bit. Christoph also correctly points out that this makes codepaths (e.g. ioctls) way easier to follow that would otherwise have to do more complex argument passing than necessary. Link: https://lore.kernel.org/r/20210121131959.646623-4-christian.brauner@ubuntu.com Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Suggested-by: Christoph Hellwig Reviewed-by: Christoph Hellwig Reviewed-by: James Morris Signed-off-by: Christian Brauner --- fs/init.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs/init.c') diff --git a/fs/init.c b/fs/init.c index e9c320a48cf1..02723bea8499 100644 --- a/fs/init.c +++ b/fs/init.c @@ -49,7 +49,7 @@ int __init init_chdir(const char *filename) error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path); if (error) return error; - error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR); + error = path_permission(&path, MAY_EXEC | MAY_CHDIR); if (!error) set_fs_pwd(current->fs, &path); path_put(&path); @@ -64,7 +64,7 @@ int __init init_chroot(const char *filename) error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path); if (error) return error; - error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR); + error = path_permission(&path, MAY_EXEC | MAY_CHDIR); if (error) goto dput_and_out; error = -EPERM; @@ -118,7 +118,7 @@ int __init init_eaccess(const char *filename) error = kern_path(filename, LOOKUP_FOLLOW, &path); if (error) return error; - error = inode_permission(d_inode(path.dentry), MAY_ACCESS); + error = path_permission(&path, MAY_ACCESS); path_put(&path); return error; } -- cgit v1.2.3 From ba73d98745be1c10dc3cce68e8d7b95012d07d05 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:31 +0100 Subject: namei: handle idmapped mounts in may_*() helpers The may_follow_link(), may_linkat(), may_lookup(), may_open(), may_o_create(), may_create_in_sticky(), may_delete(), and may_create() helpers determine whether the caller is privileged enough to perform the associated operations. Let them handle idmapped mounts by mapping the inode or fsids according to the mount's user namespace. Afterwards the checks are identical to non-idmapped inodes. The patch takes care to retrieve the mount's user namespace right before performing permission checks and passing it down into the fileystem so the user namespace can't change in between by someone idmapping a mount that is currently not idmapped. 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/20210121131959.646623-13-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/init.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/init.c') diff --git a/fs/init.c b/fs/init.c index 02723bea8499..891284f8a443 100644 --- a/fs/init.c +++ b/fs/init.c @@ -181,7 +181,7 @@ int __init init_link(const char *oldname, const char *newname) error = -EXDEV; if (old_path.mnt != new_path.mnt) goto out_dput; - error = may_linkat(&old_path); + error = may_linkat(&init_user_ns, &old_path); if (unlikely(error)) goto out_dput; error = security_path_link(old_path.dentry, &new_path, new_dentry); -- cgit v1.2.3 From 6521f8917082928a4cb637eb64b77b5f2f5b30fc Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:33 +0100 Subject: namei: prepare for idmapped mounts The various vfs_*() helpers are called by filesystems or by the vfs itself to perform core operations such as create, link, mkdir, mknod, rename, rmdir, tmpfile and unlink. Enable them to handle idmapped mounts. If the inode is accessed through an idmapped mount map it into the mount's user namespace and pass it down. Afterwards the checks and operations 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. Link: https://lore.kernel.org/r/20210121131959.646623-15-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/init.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) (limited to 'fs/init.c') diff --git a/fs/init.c b/fs/init.c index 891284f8a443..e65452750fa5 100644 --- a/fs/init.c +++ b/fs/init.c @@ -157,8 +157,8 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev) mode &= ~current_umask(); error = security_path_mknod(&path, dentry, mode, dev); if (!error) - error = vfs_mknod(path.dentry->d_inode, dentry, mode, - new_decode_dev(dev)); + error = vfs_mknod(&init_user_ns, path.dentry->d_inode, dentry, + mode, new_decode_dev(dev)); done_path_create(&path, dentry); return error; } @@ -187,8 +187,8 @@ int __init init_link(const char *oldname, const char *newname) error = security_path_link(old_path.dentry, &new_path, new_dentry); if (error) goto out_dput; - error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, - NULL); + error = vfs_link(old_path.dentry, &init_user_ns, + new_path.dentry->d_inode, new_dentry, NULL); out_dput: done_path_create(&new_path, new_dentry); out: @@ -207,7 +207,8 @@ int __init init_symlink(const char *oldname, const char *newname) return PTR_ERR(dentry); error = security_path_symlink(&path, dentry, oldname); if (!error) - error = vfs_symlink(path.dentry->d_inode, dentry, oldname); + error = vfs_symlink(&init_user_ns, path.dentry->d_inode, dentry, + oldname); done_path_create(&path, dentry); return error; } @@ -230,7 +231,8 @@ int __init init_mkdir(const char *pathname, umode_t mode) mode &= ~current_umask(); error = security_path_mkdir(&path, dentry, mode); if (!error) - error = vfs_mkdir(path.dentry->d_inode, dentry, mode); + error = vfs_mkdir(&init_user_ns, path.dentry->d_inode, dentry, + mode); done_path_create(&path, dentry); return error; } -- cgit v1.2.3 From b816dd5ddeae3252bb4255105b4c641e4c841501 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 21 Jan 2021 14:19:39 +0100 Subject: init: handle idmapped mounts Enable the init helpers to handle idmapped mounts by passing down the mount's user namespace. 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/20210121131959.646623-21-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/init.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) (limited to 'fs/init.c') diff --git a/fs/init.c b/fs/init.c index e65452750fa5..5c36adaa9b44 100644 --- a/fs/init.c +++ b/fs/init.c @@ -157,8 +157,8 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev) mode &= ~current_umask(); error = security_path_mknod(&path, dentry, mode, dev); if (!error) - error = vfs_mknod(&init_user_ns, path.dentry->d_inode, dentry, - mode, new_decode_dev(dev)); + error = vfs_mknod(mnt_user_ns(path.mnt), path.dentry->d_inode, + dentry, mode, new_decode_dev(dev)); done_path_create(&path, dentry); return error; } @@ -167,6 +167,7 @@ int __init init_link(const char *oldname, const char *newname) { struct dentry *new_dentry; struct path old_path, new_path; + struct user_namespace *mnt_userns; int error; error = kern_path(oldname, 0, &old_path); @@ -181,14 +182,15 @@ int __init init_link(const char *oldname, const char *newname) error = -EXDEV; if (old_path.mnt != new_path.mnt) goto out_dput; - error = may_linkat(&init_user_ns, &old_path); + mnt_userns = mnt_user_ns(new_path.mnt); + error = may_linkat(mnt_userns, &old_path); if (unlikely(error)) goto out_dput; error = security_path_link(old_path.dentry, &new_path, new_dentry); if (error) goto out_dput; - error = vfs_link(old_path.dentry, &init_user_ns, - new_path.dentry->d_inode, new_dentry, NULL); + error = vfs_link(old_path.dentry, mnt_userns, new_path.dentry->d_inode, + new_dentry, NULL); out_dput: done_path_create(&new_path, new_dentry); out: @@ -207,8 +209,8 @@ int __init init_symlink(const char *oldname, const char *newname) return PTR_ERR(dentry); error = security_path_symlink(&path, dentry, oldname); if (!error) - error = vfs_symlink(&init_user_ns, path.dentry->d_inode, dentry, - oldname); + error = vfs_symlink(mnt_user_ns(path.mnt), path.dentry->d_inode, + dentry, oldname); done_path_create(&path, dentry); return error; } @@ -231,8 +233,8 @@ int __init init_mkdir(const char *pathname, umode_t mode) mode &= ~current_umask(); error = security_path_mkdir(&path, dentry, mode); if (!error) - error = vfs_mkdir(&init_user_ns, path.dentry->d_inode, dentry, - mode); + error = vfs_mkdir(mnt_user_ns(path.mnt), path.dentry->d_inode, + dentry, mode); done_path_create(&path, dentry); return error; } -- cgit v1.2.3