Messages in this thread | | | Date | Mon, 13 Nov 2006 17:28:49 -0800 | From | suzuki <> | Subject | Re: + fix-compat-space-msg-size-limit-for-msgsnd-msgrcv.patch added to -mm tree |
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Arnd Bergmann wrote: > On Tuesday 14 November 2006 00:58, akpm@osdl.org wrote: > > >>Subject: Fix compat space msg size limit for msgsnd/msgrcv >>From: suzuki <suzuki@linux.vnet.ibm.com> >> >>Currently we allocate 64k space on the user stack and use it the msgbuf for >>sys_{msgrcv,msgsnd} for compat and the results are later copied in user [by >>copy_in_user]. >> >>This patch introduces helper routines for sys_{msgrcv,msgsnd} which would >>accept the pointer to msgbuf along with the msgp->mtext. This avoids the >>need to allocate the msgsize on the userspace (thus removing the size >>limit) and the overhead of an extra copy_in_user(). >> >>Signed-off-by: Suzuki K P <suzuki@in.ibm.com> >>Cc: Arnd Bergmann <arnd@arndb.de> >>Cc: "David S. Miller" <davem@davemloft.net> >>Signed-off-by: Andrew Morton <akpm@osdl.org> >
> > This patch is definitely a big step in the right direction here, but why > not go all the way and pass msgp->mtype to do_msgsnd/do_msgrcv as kernel > data instead of a user space pointer? This way you can get rid of the > compat_alloc_userspace entirely and save avoid doing an extra > put_user/get_user pair in the compat_ function. >
I left it as such, inorder to avoid the future changes that may come in the struct msgbuf -if at all-, which would make us to pass every single field as a parameter to do_msgrcv/do_msgsnd.
thanks,
Suzuki > Arnd <><
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