Re: [Qemu-devel] [PATCH QEMU v1 1/4] multiboot: bss_end_addr can be zero

[P J P]

+-- On Thu, 21 Dec 2017, Jack Schwartz wrote --+
| The multiboot spec (https://www.gnu.org/software/grub/manual/multiboot/),
| section 3.1.3, allows for bss_end_addr to be zero.
| 
| A zero bss_end_addr signifies there is no .bss section.
| 
| Suggested-by: Daniel Kiper 
| Signed-off-by: Jack Schwartz 
| Reviewed-by: Daniel Kiper 
| ---
|  hw/i386/multiboot.c | 18 ++
|  1 file changed, 10 insertions(+), 8 deletions(-)
| 
| diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
| index c7b70c9..ff2733d 100644
| --- a/hw/i386/multiboot.c
| +++ b/hw/i386/multiboot.c
| @@ -233,12 +233,6 @@ int load_multiboot(FWCfgState *fw_cfg,
|  mh_entry_addr = ldl_p(header+i+28);
|  
|  if (mh_load_end_addr) {
| -if (mh_bss_end_addr < mh_load_addr) {
| -fprintf(stderr, "invalid mh_bss_end_addr address\n");
| -exit(1);
| -}
| -mb_kernel_size = mh_bss_end_addr - mh_load_addr;
| -
|  if (mh_load_end_addr < mh_load_addr) {
|  fprintf(stderr, "invalid mh_load_end_addr address\n");
|  exit(1);
| @@ -249,8 +243,16 @@ int load_multiboot(FWCfgState *fw_cfg,
|  fprintf(stderr, "invalid kernel_file_size\n");
|  exit(1);
|  }
| -mb_kernel_size = kernel_file_size - mb_kernel_text_offset;
| -mb_load_size = mb_kernel_size;
| +mb_load_size = kernel_file_size - mb_kernel_text_offset;
| +}
| +if (mh_bss_end_addr) {
| +if (mh_bss_end_addr < (mh_load_addr + mb_load_size)) {
| +fprintf(stderr, "invalid mh_bss_end_addr address\n");
| +exit(1);
| +}
| +mb_kernel_size = mh_bss_end_addr - mh_load_addr;
| +} else {
| +mb_kernel_size = mb_load_size;
|  }
|  
|  /* Valid if mh_flags sets MULTIBOOT_HEADER_HAS_VBE.

Looks good.
Reviewed-by: Prasad J Pandit 

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F

[Qemu-devel] [PATCH QEMU v1 1/4] multiboot: bss_end_addr can be zero

[Jack Schwartz]

The multiboot spec (https://www.gnu.org/software/grub/manual/multiboot/),
section 3.1.3, allows for bss_end_addr to be zero.

A zero bss_end_addr signifies there is no .bss section.

Suggested-by: Daniel Kiper 
Signed-off-by: Jack Schwartz 
Reviewed-by: Daniel Kiper 
---
 hw/i386/multiboot.c | 18 ++
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
index c7b70c9..ff2733d 100644
--- a/hw/i386/multiboot.c
+++ b/hw/i386/multiboot.c
@@ -233,12 +233,6 @@ int load_multiboot(FWCfgState *fw_cfg,
 mh_entry_addr = ldl_p(header+i+28);
 
 if (mh_load_end_addr) {
-if (mh_bss_end_addr < mh_load_addr) {
-fprintf(stderr, "invalid mh_bss_end_addr address\n");
-exit(1);
-}
-mb_kernel_size = mh_bss_end_addr - mh_load_addr;
-
 if (mh_load_end_addr < mh_load_addr) {
 fprintf(stderr, "invalid mh_load_end_addr address\n");
 exit(1);
@@ -249,8 +243,16 @@ int load_multiboot(FWCfgState *fw_cfg,
 fprintf(stderr, "invalid kernel_file_size\n");
 exit(1);
 }
-mb_kernel_size = kernel_file_size - mb_kernel_text_offset;
-mb_load_size = mb_kernel_size;
+mb_load_size = kernel_file_size - mb_kernel_text_offset;
+}
+if (mh_bss_end_addr) {
+if (mh_bss_end_addr < (mh_load_addr + mb_load_size)) {
+fprintf(stderr, "invalid mh_bss_end_addr address\n");
+exit(1);
+}
+mb_kernel_size = mh_bss_end_addr - mh_load_addr;
+} else {
+mb_kernel_size = mb_load_size;
 }
 
 /* Valid if mh_flags sets MULTIBOOT_HEADER_HAS_VBE.
-- 
1.8.3.1