@@ -84,6 +84,9 @@ static MemoryRegion io_mem_unassigned;
*/
#define RAM_RESIZEABLE (1 << 2)
+/* An extra page is mapped on top of this RAM.
+ */
+#define RAM_EXTRA (1 << 3)
#endif
struct CPUTailQ cpus = QTAILQ_HEAD_INITIALIZER(cpus);
@@ -1185,10 +1188,13 @@ static void *file_ram_alloc(RAMBlock *block,
char *filename;
char *sanitized_name;
char *c;
+ void *ptr;
void *area = NULL;
int fd;
uint64_t hpagesize;
+ uint64_t total;
Error *local_err = NULL;
+ size_t offset;
hpagesize = gethugepagesize(path, &local_err);
if (local_err) {
@@ -1232,6 +1238,7 @@ static void *file_ram_alloc(RAMBlock *block,
g_free(filename);
memory = ROUND_UP(memory, hpagesize);
+ total = memory + hpagesize;
/*
* ftruncate is not supported by hugetlbfs in older
@@ -1243,16 +1250,40 @@ static void *file_ram_alloc(RAMBlock *block,
perror("ftruncate");
}
- area = mmap(0, memory, PROT_READ | PROT_WRITE,
- (block->flags & RAM_SHARED ? MAP_SHARED : MAP_PRIVATE),
+ ptr = mmap(0, total, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0);
+ if (ptr == MAP_FAILED) {
+ error_setg_errno(errp, errno,
+ "unable to allocate memory range for hugepages");
+ close(fd);
+ goto error;
+ }
+
+ offset = QEMU_ALIGN_UP((uintptr_t)ptr, hpagesize) - (uintptr_t)ptr;
+
+ area = mmap(ptr + offset, memory, PROT_READ | PROT_WRITE,
+ (block->flags & RAM_SHARED ? MAP_SHARED : MAP_PRIVATE) |
+ MAP_FIXED,
fd, 0);
if (area == MAP_FAILED) {
error_setg_errno(errp, errno,
"unable to map backing store for hugepages");
+ munmap(ptr, total);
close(fd);
goto error;
}
+ if (offset > 0) {
+ munmap(ptr, offset);
+ }
+ ptr += offset;
+ total -= offset;
+
+ if (total > memory + getpagesize()) {
+ munmap(ptr + memory + getpagesize(),
+ total - memory - getpagesize());
+ }
+
if (mem_prealloc) {
os_mem_prealloc(fd, area, memory);
}
@@ -1570,6 +1601,7 @@ ram_addr_t qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
new_block->used_length = size;
new_block->max_length = size;
new_block->flags = share ? RAM_SHARED : 0;
+ new_block->flags |= RAM_EXTRA;
new_block->host = file_ram_alloc(new_block, size,
mem_path, errp);
if (!new_block->host) {
@@ -1671,7 +1703,11 @@ static void reclaim_ramblock(RAMBlock *block)
xen_invalidate_map_cache_entry(block->host);
#ifndef _WIN32
} else if (block->fd >= 0) {
- munmap(block->host, block->max_length);
+ if (block->flags & RAM_EXTRA) {
+ munmap(block->host, block->max_length + getpagesize());
+ } else {
+ munmap(block->host, block->max_length);
+ }
close(block->fd);
#endif
} else {
This inserts a read and write protected page between RAM and QEMU memory, for file-backend RAM. This makes it harder to exploit QEMU bugs resulting from buffer overflows in devices using variants of cpu_physical_memory_map, dma_memory_map etc. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- exec.c | 42 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 39 insertions(+), 3 deletions(-)