Re: [PATCH] {linux,bsd}-user: Fail mmap() if size doesn't fit into host's size_t

[Warner Losh]

On Thu, Jan 25, 2024 at 1:07 PM Ilya Leoshkevich <iii@linux.ibm.com> wrote:

s390x's branch-relative-long test fails with the following error
message on 32-bit hosts:

    qemu-s390x: ../accel/tcg/user-exec.c:493: page_set_flags: Assertion `last <= GUEST_ADDR_MAX' failed.

The root cause is that the size passed to mmap() by this test does not
fit into 32 bits and gets truncated. Since there is no chance for such
mmap() to succeed, detect this condition and fail the mmap() right away.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 bsd-user/mmap.c   | 4 ++++
 linux-user/mmap.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/bsd-user/mmap.c b/bsd-user/mmap.c
index 3ef11b28079..5dc327d0ad3 100644
--- a/bsd-user/mmap.c
+++ b/bsd-user/mmap.c
@@ -256,6 +256,10 @@ static abi_ulong mmap_find_vma_aligned(abi_ulong start, abi_ulong size,

     size = HOST_PAGE_ALIGN(size);

+    if (size != (size_t)size) {
+        return (abi_ulong)(-1);
+    }
+
     if (reserved_va) {
         return mmap_find_vma_reserved(start, size,
             (alignment != 0 ? 1 << alignment :

Reviewed-by: Warner Losh <imp@bsdimp.com>

Seems good to me..  I can queue it to this month's landing code, unless Richard beats me to it.

Warner