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fuse: setattr should set FATTR_KILL_SUIDGID

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If fc->handle_killpriv_v2 is enabled, we expect file server to clear
suid/sgid/security.capbility upon chown/truncate/write as appropriate.

Upon truncate (ATTR_SIZE), suid/sgid are cleared only if caller does not
have CAP_FSETID.  File server does not know whether caller has CAP_FSETID
or not.  Hence set FATTR_KILL_SUIDGID upon truncate to let file server know
that caller does not have CAP_FSETID and it should kill suid/sgid as
appropriate.

On chown (ATTR_UID/ATTR_GID) suid/sgid need to be cleared irrespective of
capabilities of calling process, so set FATTR_KILL_SUIDGID unconditionally
in that case.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Vivek Goyal
2020-10-09 14:15:09 -04:00
committed by Miklos Szeredi
parent b866739596
commit 3179216135
2 changed files with 12 additions and 1 deletions
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3
include/uapi/linux/fuse.h
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@@ -177,7 +177,7 @@
* - add flags to fuse_attr, add FUSE_ATTR_SUBMOUNT, add FUSE_SUBMOUNTS
*
* 7.33
* - add FUSE_HANDLE_KILLPRIV_V2, FUSE_WRITE_KILL_SUIDGID
* - add FUSE_HANDLE_KILLPRIV_V2, FUSE_WRITE_KILL_SUIDGID, FATTR_KILL_SUIDGID
*/
#ifndef _LINUX_FUSE_H
@@ -274,6 +274,7 @@ struct fuse_file_lock {
#define FATTR_MTIME_NOW (1 << 8)
#define FATTR_LOCKOWNER (1 << 9)
#define FATTR_CTIME (1 << 10)
#define FATTR_KILL_SUIDGID (1 << 11)
/**
* Flags returned by the OPEN request