From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50249) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bLAXp-0003no-2q for qemu-devel@nongnu.org; Thu, 07 Jul 2016 10:44:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bLAXn-0006Am-5y for qemu-devel@nongnu.org; Thu, 07 Jul 2016 10:44:48 -0400 Received: from orth.archaic.org.uk ([2001:8b0:1d0::2]:58124) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bLAXm-0006A9-Tv for qemu-devel@nongnu.org; Thu, 07 Jul 2016 10:44:47 -0400 From: Peter Maydell Date: Thu, 7 Jul 2016 15:44:43 +0100 Message-Id: <1467902683-12904-1-git-send-email-peter.maydell@linaro.org> Subject: [Qemu-devel] [PATCH] linux-user: Handle short lengths in host_to_target_sockaddr() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: patches@linaro.org, Riku Voipio 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 --- 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