hw/elf_ops: clear uninitialized segment space

When the mem_size of the segment is bigger than the file_size,
and if this space doesn't overlap another segment, it needs
to be cleared.

This bug is very similar to the one we had for linux-user,
22d113b52f41 ("linux-user: Fix loading of BSS segments"),
where .bss section is encoded as an extension of the the data
one by setting the segment p_memsz > p_filesz.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
[PMD: Use recently added address_space_set()]
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220115203725.3834712-3-laurent@vivier.eu>

2 files changed, 17 insertions, 0 deletions

diff --git a/hw/core/loader.c b/hw/core/loader.c
index 052a0fd719..19edb928e9 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -1164,9 +1164,13 @@ static void rom_reset(void *unused)
         if (rom->mr) {
             void *host = memory_region_get_ram_ptr(rom->mr);
             memcpy(host, rom->data, rom->datasize);
+            memset(host + rom->datasize, 0, rom->romsize - rom->datasize);
         } else {
             address_space_write_rom(rom->as, rom->addr, MEMTXATTRS_UNSPECIFIED,
                                     rom->data, rom->datasize);
+            address_space_set(rom->as, rom->addr + rom->datasize, 0,
+                              rom->romsize - rom->datasize,
+                              MEMTXATTRS_UNSPECIFIED);
         }
         if (rom->isrom) {
             /* rom needs to be written only once */
diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h
index 995de8495c..7c3b1d0f6c 100644
--- a/include/hw/elf_ops.h
+++ b/include/hw/elf_ops.h
@@ -555,6 +555,19 @@ static ssize_t glue(load_elf, SZ)(const char *name, int fd,
                     if (res != MEMTX_OK) {
                         goto fail;
                     }
+                    /*
+                     * We need to zero'ify the space that is not copied
+                     * from file
+                     */
+                    if (file_size < mem_size) {
+                        res = address_space_set(as ? as : &address_space_memory,
+                                                addr + file_size, 0,
+                                                mem_size - file_size,
+                                                MEMTXATTRS_UNSPECIFIED);
+                        if (res != MEMTX_OK) {
+                            goto fail;
+                        }
+                    }
                 }
             }