From f18c69cfc554cf9776eb3c35b7510e17541afacb Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 25 Mar 2015 14:14:56 +0100 Subject: [PATCH] exec: avoid possible overwriting of mmaped area in qemu_ram_remap It is not necessary to munmap an area before remapping it with MAP_FIXED; if the memory region specified by addr and len overlaps pages of any existing mapping, then the overlapped part of the existing mapping will be discarded. On the other hand, if QEMU does munmap the pages, there is a small probability that another mmap sneaks in and catches the just-freed portion of the address space. In effect, munmap followed by mmap(MAP_FIXED) is a use-after-free error, and Coverity flags it as such. Fix it. Reviewed-by: Gonglei Signed-off-by: Paolo Bonzini --- exec.c | 1 - 1 file changed, 1 deletion(-) diff --git a/exec.c b/exec.c index 8b922db612..6d1e1e4c75 100644 --- a/exec.c +++ b/exec.c @@ -1638,7 +1638,6 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length) abort(); } else { flags = MAP_FIXED; - munmap(vaddr, length); if (block->fd >= 0) { flags |= (block->flags & RAM_SHARED ? MAP_SHARED : MAP_PRIVATE);