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From: Christian Brauner <brauner@kernel.org>
To: Christoph Hellwig <hch@lst.de>, Chris Mason <clm@fb.com>,
	Josef Bacik <josef@toxicpanda.com>,
	David Sterba <dsterba@suse.com>,
	Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-btrfs@vger.kernel.org,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Christoph Hellwig <hch@infradead.org>
Subject: [PATCH v2 12/21] btrfs/ioctl: check whether fs{g,u}id are mapped during subvolume creation
Date: Mon, 19 Jul 2021 13:10:43 +0200	[thread overview]
Message-ID: <20210719111052.1626299-13-brauner@kernel.org> (raw)
In-Reply-To: <20210719111052.1626299-1-brauner@kernel.org>

From: Christian Brauner <christian.brauner@ubuntu.com>

When a new subvolume is created btrfs currently doesn't check whether the
fs{g,u}id of the caller actually have a mapping in the user namespace attached
to the filesystem. The vfs always checks this to make sure that the caller's
fs{g,u}id can be represented on-disk. This is most relevant for filesystems
that can be mounted inside user namespaces but it is in general a good
hardening measure to prevent unrepresentable {g,u}ids from being written to
disk.
Since we want to support idmapped mounts for btrfs ioctls to create subvolumes
in follow-up patches this becomes important since we want to make sure the
fs{g,u}id of the caller as mapped according to the idmapped mount can be
represented on-disk. Simply add the missing fsuidgid_has_mapping() line from
the vfs may_create() version to btrfs_may_create().

Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Sterba <dsterba@suse.com>
Cc: linux-btrfs@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
unchanged
---
 fs/btrfs/ioctl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0ba98e08a029..7a6a886df7c4 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -870,6 +870,8 @@ static inline int btrfs_may_create(struct inode *dir, struct dentry *child)
 		return -EEXIST;
 	if (IS_DEADDIR(dir))
 		return -ENOENT;
+	if (!fsuidgid_has_mapping(dir->i_sb, &init_user_ns))
+		return -EOVERFLOW;
 	return inode_permission(&init_user_ns, dir, MAY_WRITE | MAY_EXEC);
 }
 
-- 
2.30.2


  parent reply	other threads:[~2021-07-19 11:11 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-19 11:10 [PATCH v2 00/21] btrfs: support idmapped mounts Christian Brauner
2021-07-19 11:10 ` [PATCH v2 01/21] namei: add mapping aware lookup helper Christian Brauner
2021-07-19 11:10 ` [PATCH v2 02/21] btrfs/inode: handle idmaps in btrfs_new_inode() Christian Brauner
2021-07-19 11:10 ` [PATCH v2 03/21] btrfs/inode: allow idmapped rename iop Christian Brauner
2021-07-19 11:10 ` [PATCH v2 04/21] btrfs/inode: allow idmapped getattr iop Christian Brauner
2021-07-19 11:10 ` [PATCH v2 05/21] btrfs/inode: allow idmapped mknod iop Christian Brauner
2021-07-19 11:10 ` [PATCH v2 06/21] btrfs/inode: allow idmapped create iop Christian Brauner
2021-07-19 11:10 ` [PATCH v2 07/21] btrfs/inode: allow idmapped mkdir iop Christian Brauner
2021-07-19 11:10 ` [PATCH v2 08/21] btrfs/inode: allow idmapped symlink iop Christian Brauner
2021-07-19 11:10 ` [PATCH v2 09/21] btrfs/inode: allow idmapped tmpfile iop Christian Brauner
2021-07-19 11:10 ` [PATCH v2 10/21] btrfs/inode: allow idmapped setattr iop Christian Brauner
2021-07-19 11:10 ` [PATCH v2 11/21] btrfs/inode: allow idmapped permission iop Christian Brauner
2021-07-19 11:10 ` Christian Brauner [this message]
2021-07-19 11:10 ` [PATCH v2 13/21] btrfs/inode: allow idmapped BTRFS_IOC_{SNAP,SUBVOL}_CREATE{_V2} ioctl Christian Brauner
2021-07-19 11:10 ` [PATCH v2 14/21] btrfs/ioctl: allow idmapped BTRFS_IOC_SNAP_DESTROY{_V2} ioctl Christian Brauner
2021-07-21 14:15   ` David Sterba
2021-07-21 15:48     ` Christian Brauner
2021-07-19 11:10 ` [PATCH v2 15/21] btrfs/ioctl: relax restrictions for BTRFS_IOC_SNAP_DESTROY_V2 with subvolids Christian Brauner
2021-07-19 11:10 ` [PATCH v2 16/21] btrfs/ioctl: allow idmapped BTRFS_IOC_SET_RECEIVED_SUBVOL{_32} ioctl Christian Brauner
2021-07-19 11:10 ` [PATCH v2 17/21] btrfs/ioctl: allow idmapped BTRFS_IOC_SUBVOL_SETFLAGS ioctl Christian Brauner
2021-07-19 11:10 ` [PATCH v2 18/21] btrfs/ioctl: allow idmapped BTRFS_IOC_INO_LOOKUP_USER ioctl Christian Brauner
2021-07-19 11:10 ` [PATCH v2 19/21] btrfs/acl: handle idmapped mounts Christian Brauner
2021-07-19 11:10 ` [PATCH v2 20/21] btrfs/super: allow idmapped btrfs Christian Brauner
2021-07-19 11:10 ` [PATCH v2 21/21] btrfs/242: introduce btrfs specific idmapped mounts tests Christian Brauner
2021-07-19 15:11 ` [PATCH v2 00/21] btrfs: support idmapped mounts Josef Bacik

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