Messages in this thread | | | From | Richard Weinberger <> | Subject | Re: [uml-devel] [PATCH 1/1] hostfs: fix UML crash | Date | Mon, 18 Oct 2010 22:03:42 +0200 |
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Am Montag 18 Oktober 2010, 21:43:44 schrieb Geert Uytterhoeven: > On Mon, Oct 18, 2010 at 21:31, Richard Weinberger <richard@nod.at> wrote: > > Am Montag 18 Oktober 2010, 21:22:31 schrieb Geert Uytterhoeven: > >> On Mon, Oct 18, 2010 at 20:40, Andrew Morton <akpm@linux-foundation.org> > > > > wrote: > >> > On Mon, 18 Oct 2010 18:36:54 +0200 Richard Weinberger <richard@nod.at> > > > > wrote: > >> >> 365b1818 resized f_spare within struct statfs. > >> >> hostfs accesses f_spare directly and needs an update. > >> >> > >> >> Signed-off-by: Richard Weinberger <richard@nod.at> > >> >> Reported-by: Toralf F__rster <toralf.foerster@gmx.de> > >> >> Tested-by: Toralf F__rster <toralf.foerster@gmx.de> > >> >> --- > >> >> 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...
IMHO using kstatfs within ubd_user.c is not very nice because is a internal kernel struct.
> > Anyway, why do we need to copy f_spare from the host to the guest? > > I'm quite sure it can be omitted. > > I guess it wants to preserve fields that are added in the future, > which may be useful > if the host is more recent than the guest.
Good point!
Thanks, //richard
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