arm: oabi compat: add missing access checks

Add access checks to sys_oabi_epoll_wait() and sys_oabi_semtimedop().
This fixes CVE-2016-3857, a local privilege escalation under
CONFIG_OABI_COMPAT.

Cc: stable@vger.kernel.org
Reported-by: Chiachih Wu <wuchiachih@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Dave Weinstein <olorin@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm/kernel/sys_oabi-compat.c b/arch/arm/kernel/sys_oabi-compat.c
index 087acb5..5f221ac 100644 (file)
--- a/arch/arm/kernel/sys_oabi-compat.c
+++ b/arch/arm/kernel/sys_oabi-compat.c
@@ -279,8 +279,12 @@ asmlinkage long sys_oabi_epoll_wait(int epfd,
        mm_segment_t fs;
        long ret, err, i;
 
-       if (maxevents <= 0 || maxevents > (INT_MAX/sizeof(struct epoll_event)))
+       if (maxevents <= 0 ||
+                       maxevents > (INT_MAX/sizeof(*kbuf)) ||
+                       maxevents > (INT_MAX/sizeof(*events)))
                return -EINVAL;
+       if (!access_ok(VERIFY_WRITE, events, sizeof(*events) * maxevents))
+               return -EFAULT;
        kbuf = kmalloc(sizeof(*kbuf) * maxevents, GFP_KERNEL);
        if (!kbuf)
                return -ENOMEM;
@@ -317,6 +321,8 @@ asmlinkage long sys_oabi_semtimedop(int semid,
 
        if (nsops < 1 || nsops > SEMOPM)
                return -EINVAL;
+       if (!access_ok(VERIFY_READ, tsops, sizeof(*tsops) * nsops))
+               return -EFAULT;
        sops = kmalloc(sizeof(*sops) * nsops, GFP_KERNEL);
        if (!sops)
                return -ENOMEM;