From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Richard Weinberger Subject: Re: [uml-devel] [PATCH 1/1] hostfs: fix UML crash Date: Mon, 18 Oct 2010 21:31:33 +0200 References: <1287419814-20086-1-git-send-email-richard@nod.at> <20101018114039.503233da.akpm@linux-foundation.org> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201010182131.33385.richard@nod.at> To: Geert Uytterhoeven Cc: Andrew Morton , toralf.foerster@gmx.de, jdike@addtoit.com, linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net, viro@zeniv.linux.org.uk List-ID: Am Montag 18 Oktober 2010, 21:22:31 schrieb Geert Uytterhoeven: > On Mon, Oct 18, 2010 at 20:40, Andrew Morton wrote: > > On Mon, 18 Oct 2010 18:36:54 +0200 Richard Weinberger wrote: > >> 365b1818 resized f_spare within struct statfs. > >> hostfs accesses f_spare directly and needs an update. > >> > >> Signed-off-by: Richard Weinberger > >> Reported-by: Toralf F__rster > >> Tested-by: Toralf F__rster > >> --- > >> fs/hostfs/hostfs_user.c | 2 +- > >> 1 files changed, 1 insertions(+), 1 deletions(-) > >> > >> diff --git a/fs/hostfs/hostfs_user.c b/fs/hostfs/hostfs_user.c > >> index 6777aa0..ce2f168 100644 > >> --- a/fs/hostfs/hostfs_user.c > >> +++ b/fs/hostfs/hostfs_user.c > >> @@ -388,6 +388,6 @@ int do_statfs(char *root, long *bsize_out, long long > >> *blocks_out, spare_out[1] = buf.f_spare[1]; > >> spare_out[2] = buf.f_spare[2]; > >> spare_out[3] = buf.f_spare[3]; > >> - spare_out[4] = buf.f_spare[4]; > >> + > >> return 0; > >> } > > > > Thanks. > > > > Is there any reason for hostfs to be playing with the f_spare field at > > all? > > It just copies it from struct statfs64 on the host to struct kstatfs > on the guest. > Probably a memcpy() is more future-safe, if it's combined with a > BUILD_BUG_ON(sizeof(statfs64.f_spare) != sizeof(kstatfs.f_spare)). > > Still, currently it doesn't copy the recently added f_flags field. > To protect against future changes like that, an explicit > BUILD_BUG_ON(sizeof(kstatfs.f_spare) != 4*sizeof(long)) may be even > better... Anyway, why do we need to copy f_spare from the host to the guest? I'm quite sure it can be omitted. Thanks, //richard