Comment 11 for bug 1783362

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 <email address hidden>
Cc: umarcor <email address hidden>

---
v2
  - add comment on overflow
---
 linux-user/mmap.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index d0c50e4888..41e0983ce8 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;

--
2.17.1