Hi Prasad.

The Multiboot Spec will allow for a zero bss end address.  (Please see section 3.1.3 at https://www.gnu.org/software/grub/manual/multiboot/  . ) For a zero bss end address, this patch will not do the right thing.

I had proposed some patches to properly handle zero bss end address, but they got delayed.  However, I will be re-sending updated patches out later today.  Please stay tuned...


On 02/27/18 11:48, P J P wrote:
From: Prasad J Pandit <p...@fedoraproject.org>

While loading kernel via multiboot-v1 image, (flags & 0x00010000)
indicates that multiboot header contains valid addresses to load
the kernel image. In that, end of the data segment address
'mh_load_end_addr' should be less than the bss segment address
'mh_bss_end_addr'. Add check to validate that.

Reported-by: CERT CC <cert...@orange.com>
Signed-off-by: Prasad J Pandit <p...@fedoraproject.org>
  hw/i386/multiboot.c | 4 ++++
  1 file changed, 4 insertions(+)

diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
index 46d9c68bf5..d16e32bf4a 100644
--- a/hw/i386/multiboot.c
+++ b/hw/i386/multiboot.c
@@ -227,6 +227,10 @@ int load_multiboot(FWCfgState *fw_cfg,
              fprintf(stderr, "invalid mh_load_addr address\n");
+        if (mh_load_end_addr > mh_bss_end_addr) {
+            fprintf(stderr, "invalid mh_load_end_addr address\n");
+            exit(1);
+        }
uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
          uint32_t mb_load_size = 0;

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