From be3bd286bc06bb68cdc71748d9dd4edcd57b2b24 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 15 May 2014 14:40:23 +0100 Subject: [PATCH] linux-user: Don't overrun guest buffer in sched_getaffinity If the guest's "long" type is smaller than the host's, then our sched_getaffinity wrapper needs to round the buffer size up to a multiple of the host sizeof(long). This means that when we copy the data back from the host buffer to the guest's buffer there might be more than we can fit. Rather than overflowing the guest's buffer, handle this case by returning EINVAL or ignoring the unused extra space, as appropriate. Note that only guests using the syscall interface directly might run into this bug -- the glibc wrappers around it will always use a buffer whose size is a multiple of 8 regardless of guest architecture. Signed-off-by: Peter Maydell Signed-off-by: Riku Voipio --- linux-user/syscall.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 6efeeff2bf..840ced1fda 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -7438,6 +7438,22 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, ret = get_errno(sys_sched_getaffinity(arg1, mask_size, mask)); if (!is_error(ret)) { + if (ret > arg2) { + /* More data returned than the caller's buffer will fit. + * This only happens if sizeof(abi_long) < sizeof(long) + * and the caller passed us a buffer holding an odd number + * of abi_longs. If the host kernel is actually using the + * extra 4 bytes then fail EINVAL; otherwise we can just + * ignore them and only copy the interesting part. + */ + int numcpus = sysconf(_SC_NPROCESSORS_CONF); + if (numcpus > arg2 * 8) { + ret = -TARGET_EINVAL; + break; + } + ret = arg2; + } + if (copy_to_user(arg3, mask, ret)) { goto efault; }