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Re: [Qemu-devel] [PATCH] linux-user: Handle short lengths in host_to_tar
From: |
Riku Voipio |
Subject: |
Re: [Qemu-devel] [PATCH] linux-user: Handle short lengths in host_to_target_sockaddr() |
Date: |
Thu, 7 Jul 2016 22:23:22 +0300 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Thu, Jul 07, 2016 at 03:44:43PM +0100, Peter Maydell wrote:
> If userspace specifies a short buffer for a target sockaddr,
> the kernel will only copy in as much as it has space for
> (or none at all if the length is zero) -- see the kernel
> move_addr_to_user() function. Mimic this in QEMU's
> host_to_target_sockaddr() routine.
>
> In particular, this fixes a segfault running the LTP
> recvfrom01 test, where the guest makes a recvfrom()
> call with a bad buffer pointer and other parameters which
> cause the kernel to set the addrlen to zero; because we
> did not skip the attempt to swap the sa_family field we
> segfaulted on the bad address.
> Signed-off-by: Peter Maydell <address@hidden>
All your patches up to this one applied to linux-user, thanks!
Riku
> ---
> linux-user/syscall.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 165fd06..6e77d34 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -1374,12 +1374,19 @@ static inline abi_long
> host_to_target_sockaddr(abi_ulong target_addr,
> {
> struct target_sockaddr *target_saddr;
>
> + if (len == 0) {
> + return 0;
> + }
> +
> target_saddr = lock_user(VERIFY_WRITE, target_addr, len, 0);
> if (!target_saddr)
> return -TARGET_EFAULT;
> memcpy(target_saddr, addr, len);
> - target_saddr->sa_family = tswap16(addr->sa_family);
> - if (addr->sa_family == AF_NETLINK) {
> + if (len >= offsetof(struct target_sockaddr, sa_family) +
> + sizeof(target_saddr->sa_family)) {
> + target_saddr->sa_family = tswap16(addr->sa_family);
> + }
> + if (addr->sa_family == AF_NETLINK && len >= sizeof(struct sockaddr_nl)) {
> struct sockaddr_nl *target_nl = (struct sockaddr_nl *)target_saddr;
> target_nl->nl_pid = tswap32(target_nl->nl_pid);
> target_nl->nl_groups = tswap32(target_nl->nl_groups);
> --
> 1.9.1
>