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Re: [Qemu-devel] [PATCH 0/2] linux-user: Fix length handling in cmsg con
From: |
Riku Voipio |
Subject: |
Re: [Qemu-devel] [PATCH 0/2] linux-user: Fix length handling in cmsg conversions |
Date: |
Sat, 06 Jun 2015 13:07:15 +0300 |
On Jun 5, 2015 6:03 PM, Peter Maydell <address@hidden> wrote:
>
> Ping?
I'll collect and review linux-user patches from the list on monday.
Riku
>
> thanks
> -- PMM
>
> On 26 May 2015 at 19:46, Peter Maydell <address@hidden> wrote:
> > This patchset fixes some problems in conversions of cmsg structures
> > in target_to_host_cmsg() (used in send/recvmsg handling). Specifically:
> >
> > * we required the msg->msg_controllen to declare the buffer
> > to have enough space for final trailing padding (we were
> > checking against CMSG_SPACE), whereas the kernel does not
> > require this, and common userspace code assumes this.
> > * we weren't correctly handling the fact that the SO_TIMESTAMP
> > payload may be larger for the target than the host
> > * we weren't marking the messages with MSG_CTRUNC when we did
> > need to truncate a message that wasn't truncated by the host,
> > but were instead logging a QEMU message; since truncation is
> > always the result of a guest giving us an insufficiently
> > sized buffer, we should report it to the guest as the kernel
> > does and don't log anything
> > * we weren't handling the possibility of the host having a
> > more restrictive alignment requirement for payload structs
> >
> > The major visible issue I wanted to fix is that glibc's "try to talk
> > to nscd" code that it will run on startup will receive a cmsg with a
> > 4 byte payload and only allocates 4 bytes for it, which was causing
> > us to do the wrong thing on architectures that need 8-alignment
> > (we dropped the cmsg and printed a diagnostic message).
> >
> >
> > Peter Maydell (2):
> > linux-user: Fix length handling in host_to_target_cmsg
> > linux-user: use __get_user and __put_user in cmsg conversions
> >
> > linux-user/syscall.c | 89
> >++++++++++++++++++++++++++++++++++++++++++----------
> > 1 file changed, 72 insertions(+), 17 deletions(-)
> >
> > --
> > 1.9.1