From mboxrd@z Thu Jan 1 00:00:00 1970 From: Amerigo Wang Subject: [V4 Patch 0/2] fix file truncations when both suid and write permissions set Date: Mon, 17 Aug 2009 03:07:36 -0400 Message-ID: <20090817071001.5913.94767.sendpatchset@localhost.localdomain> Cc: esandeen@redhat.com, eteo@redhat.com, eparis@redhat.com, Amerigo Wang , linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org, sds@tycho.nsa.gov, hirofumi@mail.parknet.co.jp, viro@zeniv.linux.org.uk To: linux-kernel@vger.kernel.org Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org When suid is set and the non-owner user has write permission, any writing into this file should be allowed and suid should be removed after that. However, current kernel only allows writing without truncations, when we do truncations on that file, we get EPERM. This is a bug. Steps to reproduce this bug: % ls -l rootdir/file1 -rwsrwsrwx 1 root root 3 Jun 25 15:42 rootdir/file1 % echo h > rootdir/file1 zsh: operation not permitted: rootdir/file1 % ls -l rootdir/file1 -rwsrwsrwx 1 root root 3 Jun 25 15:42 rootdir/file1 % echo h >> rootdir/file1 % ls -l rootdir/file1 -rwxrwxrwx 1 root root 5 Jun 25 16:34 rootdir/file1 This patch fixes it. Signed-off-by: WANG Cong Andrew, these two patches can replace the -mm patch "vfs-allow-file-truncations-when-both-suid-and-write-permissions-set.patch". Thanks!