From 257a7e212d5e518ac53bd6a02a3157cf4594c8b3 Mon Sep 17 00:00:00 2001 From: Jonathan Marler Date: Sat, 2 May 2020 10:12:25 -0600 Subject: linux-user/mmap.c: fix integer underflow in target_mremap Fixes: https://bugs.launchpad.net/bugs/1876373 This code path in mmap occurs when a page size is decreased with mremap. When a section of pages is shrunk, qemu calls mmap_reserve on the pages that were released. However, it has the diff operation reversed, subtracting the larger old_size from the smaller new_size. Instead, it should be subtracting the smaller new_size from the larger old_size. You can also see in the previous line of the change that this mmap_reserve call only occurs when old_size > new_size. Bug: https://bugs.launchpad.net/qemu/+bug/1876373 Signed-off-by: Jonathan Marler Reviewded-by: Laurent Vivier Message-Id: <20200502161225.14346-1-johnnymarler@gmail.com> Signed-off-by: Laurent Vivier --- linux-user/mmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index e378033797..caab62909e 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -708,7 +708,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size, if (prot == 0) { host_addr = mremap(g2h(old_addr), old_size, new_size, flags); if (host_addr != MAP_FAILED && reserved_va && old_size > new_size) { - mmap_reserve(old_addr + old_size, new_size - old_size); + mmap_reserve(old_addr + old_size, old_size - new_size); } } else { errno = ENOMEM; -- cgit v1.2.3