Commit 550a7d3b authored by Vivek Goyal's avatar Vivek Goyal Committed by Miklos Szeredi
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fuse: add a flag FUSE_SETXATTR_ACL_KILL_SGID to kill SGID 



When posix access ACL is set, it can have an effect on file mode and it can
also need to clear SGID if.

- None of caller's group/supplementary groups match file owner group.
AND
- Caller is not priviliged (No CAP_FSETID).

As of now fuser server is responsible for changing the file mode as
well. But it does not know whether to clear SGID or not.

So add a flag FUSE_SETXATTR_ACL_KILL_SGID and send this info with SETXATTR
to let file server know that sgid needs to be cleared as well.

Reported-by: default avatarLuis Henriques <lhenriques@suse.de>
Signed-off-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 52a4c95f

fs/fuse/acl.c

+6 −1
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ int fuse_set_acl(struct user_namespace *mnt_userns, struct inode *inode, 
		return -EINVAL;



	if (acl) {

		unsigned int extra_flags = 0;

		/*

		 * Fuse userspace is responsible for updating access

		 * permissions in the inode, if needed. fuse_setxattr
@@ -94,7 +95,11 @@ int fuse_set_acl(struct user_namespace *mnt_userns, struct inode *inode, 
			return ret;

		}



		ret = fuse_setxattr(inode, name, value, size, 0, 0);

		if (!in_group_p(i_gid_into_mnt(&init_user_ns, inode)) &&

		    !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID))

			extra_flags |= FUSE_SETXATTR_ACL_KILL_SGID;



		ret = fuse_setxattr(inode, name, value, size, 0, extra_flags);

		kfree(value);

	} else {

		ret = fuse_removexattr(inode, name);

include/uapi/linux/fuse.h

+7 −0
Original line number Diff line number Diff line
@@ -180,6 +180,7 @@ 
 *  - add FUSE_HANDLE_KILLPRIV_V2, FUSE_WRITE_KILL_SUIDGID, FATTR_KILL_SUIDGID

 *  - add FUSE_OPEN_KILL_SUIDGID

 *  - extend fuse_setxattr_in, add FUSE_SETXATTR_EXT

 *  - add FUSE_SETXATTR_ACL_KILL_SGID

 */



#ifndef _LINUX_FUSE_H
@@ -454,6 +455,12 @@ struct fuse_file_lock { 
 */

#define FUSE_OPEN_KILL_SUIDGID	(1 << 0)



/**

 * setxattr flags

 * FUSE_SETXATTR_ACL_KILL_SGID: Clear SGID when system.posix_acl_access is set

 */

#define FUSE_SETXATTR_ACL_KILL_SGID	(1 << 0)



enum fuse_opcode {

	FUSE_LOOKUP		= 1,

	FUSE_FORGET		= 2,  /* no reply */