linux-user/mmap.c: handle invalid len maps correctly

I've slightly re-organised the check to more closely match the
sequence that the kernel uses in do_mmap(). We check for both the zero
case (EINVAL) and the overflow length case (ENOMEM).

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: umarcor <1783362@bugs.launchpad.net>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20180730134321.19898-2-alex.bennee@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

1 files changed, 12 insertions, 3 deletions

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index d0c50e4..41e0983 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -391,14 +391,23 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
     }
 #endif
 
-    if (offset & ~TARGET_PAGE_MASK) {
+    if (!len) {
         errno = EINVAL;
         goto fail;
     }
 
+    /* Also check for overflows... */
     len = TARGET_PAGE_ALIGN(len);
-    if (len == 0)
-        goto the_end;
+    if (!len) {
+        errno = ENOMEM;
+        goto fail;
+    }
+
+    if (offset & ~TARGET_PAGE_MASK) {
+        errno = EINVAL;
+        goto fail;
+    }
+
     real_start = start & qemu_host_page_mask;
     host_offset = offset & qemu_host_page_mask;