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Commit 5e940c1d authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

fuse: handle killpriv in userspace fs 



Only userspace filesystem can do the killing of suid/sgid without races.
So introduce an INIT flag and negotiate support for this.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent a09f99ed

fs/fuse/dir.c

+27 −17
Original line number Diff line number Diff line
@@ -1703,6 +1703,7 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr, 
static int fuse_setattr(struct dentry *entry, struct iattr *attr)

{

	struct inode *inode = d_inode(entry);

	struct fuse_conn *fc = get_fuse_conn(inode);

	struct file *file = (attr->ia_valid & ATTR_FILE) ? attr->ia_file : NULL;

	int ret;
@@ -1710,13 +1711,21 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr) 
		return -EACCES;



	if (attr->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID)) {

		int kill;



		attr->ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID |

				    ATTR_MODE);



		/*

		 * The only sane way to reliably kill suid/sgid is to do it in

		 * the userspace filesystem

		 *

		 * This should be done on write(), truncate() and chown().

		 */

		if (!fc->handle_killpriv) {

			int kill;



			/*

		 * ia_mode calculation may have used stale i_mode.  Refresh and

		 * recalculate.

			 * ia_mode calculation may have used stale i_mode.

			 * Refresh and recalculate.

			 */

			ret = fuse_do_getattr(inode, NULL, file);

			if (ret)
@@ -1733,6 +1742,7 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr) 
				attr->ia_mode &= ~S_ISGID;

			}

		}

	}

	if (!attr->ia_valid)

		return 0;

fs/fuse/fuse_i.h

+3 −0
Original line number Diff line number Diff line
@@ -547,6 +547,9 @@ struct fuse_conn { 
	/** allow parallel lookups and readdir (default is serialized) */

	unsigned parallel_dirops:1;



	/** handle fs handles killing suid/sgid/cap on write/chown/trunc */

	unsigned handle_killpriv:1;



	/*

	 * The following bitfields are only for optimization purposes

	 * and hence races in setting them will not cause malfunction

fs/fuse/inode.c

+3 −1
Original line number Diff line number Diff line
@@ -910,6 +910,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req) 
				fc->writeback_cache = 1;

			if (arg->flags & FUSE_PARALLEL_DIROPS)

				fc->parallel_dirops = 1;

			if (arg->flags & FUSE_HANDLE_KILLPRIV)

				fc->handle_killpriv = 1;

			if (arg->time_gran && arg->time_gran <= 1000000000)

				fc->sb->s_time_gran = arg->time_gran;

		} else {
@@ -941,7 +943,7 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req) 
		FUSE_FLOCK_LOCKS | FUSE_HAS_IOCTL_DIR | FUSE_AUTO_INVAL_DATA |

		FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO | FUSE_ASYNC_DIO |

		FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |

		FUSE_PARALLEL_DIROPS;

		FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV;

	req->in.h.opcode = FUSE_INIT;

	req->in.numargs = 1;

	req->in.args[0].size = sizeof(*arg);

include/uapi/linux/fuse.h

+6 −1
Original line number Diff line number Diff line
@@ -108,6 +108,9 @@ 
 *

 *  7.25

 *  - add FUSE_PARALLEL_DIROPS

 *

 *  7.26

 *  - add FUSE_HANDLE_KILLPRIV

 */



#ifndef _LINUX_FUSE_H
@@ -143,7 +146,7 @@ 
#define FUSE_KERNEL_VERSION 7



/** Minor version number of this interface */

#define FUSE_KERNEL_MINOR_VERSION 25

#define FUSE_KERNEL_MINOR_VERSION 26



/** The node ID of the root inode */

#define FUSE_ROOT_ID 1
@@ -238,6 +241,7 @@ struct fuse_file_lock { 
 * FUSE_WRITEBACK_CACHE: use writeback cache for buffered writes

 * FUSE_NO_OPEN_SUPPORT: kernel supports zero-message opens

 * FUSE_PARALLEL_DIROPS: allow parallel lookups and readdir

 * FUSE_HANDLE_KILLPRIV: fs handles killing suid/sgid/cap on write/chown/trunc

 */

#define FUSE_ASYNC_READ		(1 << 0)

#define FUSE_POSIX_LOCKS	(1 << 1)
@@ -258,6 +262,7 @@ struct fuse_file_lock { 
#define FUSE_WRITEBACK_CACHE	(1 << 16)

#define FUSE_NO_OPEN_SUPPORT	(1 << 17)

#define FUSE_PARALLEL_DIROPS    (1 << 18)

#define FUSE_HANDLE_KILLPRIV	(1 << 19)



/**

 * CUSE INIT request/reply flags