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[Qemu-devel] [PATCH] multiboot: validate multiboot header address values

P J P posted 1 patch 6 years, 7 months ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20170905174942.3094-1-ppandit@redhat.com
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hw/i386/multiboot.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
[Qemu-devel] [PATCH] multiboot: validate multiboot header address values
Posted by P J P 6 years, 7 months ago 
From: Prasad J Pandit <pjp@fedoraproject.org>

While loading kernel via multiboot-v1 image, (flags & 0x00010000)
indicates that multiboot header contains valid addresses to load
the kernel image. These addresses are used to compute kernel
size and kernel text offset in the OS image. Validate these
address values to avoid an OOB access issue.

Reported-by: Thomas Garnier <thgarnie@google.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/i386/multiboot.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
index 6001f4caa2..c7b70c91d5 100644
--- a/hw/i386/multiboot.c
+++ b/hw/i386/multiboot.c
@@ -221,15 +221,34 @@ int load_multiboot(FWCfgState *fw_cfg,
         uint32_t mh_header_addr = ldl_p(header+i+12);
         uint32_t mh_load_end_addr = ldl_p(header+i+20);
         uint32_t mh_bss_end_addr = ldl_p(header+i+24);
+
         mh_load_addr = ldl_p(header+i+16);
+        if (mh_header_addr < mh_load_addr) {
+            fprintf(stderr, "invalid mh_load_addr address\n");
+            exit(1);
+        }
+
         uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
         uint32_t mb_load_size = 0;
         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);
+            }
             mb_load_size = mh_load_end_addr - mh_load_addr;
         } else {
+            if (kernel_file_size < mb_kernel_text_offset) {
+                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;
         }
-- 
2.13.5
Re: [Qemu-devel] [PATCH] multiboot: validate multiboot header address values
Posted by Thomas Garnier via Qemu-devel 6 years, 7 months ago 
On Tue, Sep 5, 2017 at 10:49 AM, P J P <ppandit@redhat.com> wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
>
> While loading kernel via multiboot-v1 image, (flags & 0x00010000)
> indicates that multiboot header contains valid addresses to load
> the kernel image. These addresses are used to compute kernel
> size and kernel text offset in the OS image. Validate these
> address values to avoid an OOB access issue.
>
> Reported-by: Thomas Garnier <thgarnie@google.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---

Looks good, tested.

Tested-by: Thomas Garnier <thgarnie@google.com>

>  hw/i386/multiboot.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
> index 6001f4caa2..c7b70c91d5 100644
> --- a/hw/i386/multiboot.c
> +++ b/hw/i386/multiboot.c
> @@ -221,15 +221,34 @@ int load_multiboot(FWCfgState *fw_cfg,
>          uint32_t mh_header_addr = ldl_p(header+i+12);
>          uint32_t mh_load_end_addr = ldl_p(header+i+20);
>          uint32_t mh_bss_end_addr = ldl_p(header+i+24);
> +
>          mh_load_addr = ldl_p(header+i+16);
> +        if (mh_header_addr < mh_load_addr) {
> +            fprintf(stderr, "invalid mh_load_addr address\n");
> +            exit(1);
> +        }
> +
>          uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
>          uint32_t mb_load_size = 0;
>          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);
> +            }
>              mb_load_size = mh_load_end_addr - mh_load_addr;
>          } else {
> +            if (kernel_file_size < mb_kernel_text_offset) {
> +                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;
>          }
> --
> 2.13.5
>



-- 
Thomas
Re: [Qemu-devel] [PATCH] multiboot: validate multiboot header address values
Posted by Thomas Garnier via Qemu-devel 6 years, 7 months ago 
On Tue, Sep 5, 2017 at 11:12 AM, Thomas Garnier <thgarnie@google.com> wrote:
> On Tue, Sep 5, 2017 at 10:49 AM, P J P <ppandit@redhat.com> wrote:
>> From: Prasad J Pandit <pjp@fedoraproject.org>
>>
>> While loading kernel via multiboot-v1 image, (flags & 0x00010000)
>> indicates that multiboot header contains valid addresses to load
>> the kernel image. These addresses are used to compute kernel
>> size and kernel text offset in the OS image. Validate these
>> address values to avoid an OOB access issue.
>>
>> Reported-by: Thomas Garnier <thgarnie@google.com>
>> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
>> ---
>
> Looks good, tested.
>
> Tested-by: Thomas Garnier <thgarnie@google.com>

Btw, can you open a CVE for that? (and reference it in the commit).

>
>>  hw/i386/multiboot.c | 19 +++++++++++++++++++
>>  1 file changed, 19 insertions(+)
>>
>> diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
>> index 6001f4caa2..c7b70c91d5 100644
>> --- a/hw/i386/multiboot.c
>> +++ b/hw/i386/multiboot.c
>> @@ -221,15 +221,34 @@ int load_multiboot(FWCfgState *fw_cfg,
>>          uint32_t mh_header_addr = ldl_p(header+i+12);
>>          uint32_t mh_load_end_addr = ldl_p(header+i+20);
>>          uint32_t mh_bss_end_addr = ldl_p(header+i+24);
>> +
>>          mh_load_addr = ldl_p(header+i+16);
>> +        if (mh_header_addr < mh_load_addr) {
>> +            fprintf(stderr, "invalid mh_load_addr address\n");
>> +            exit(1);
>> +        }
>> +
>>          uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
>>          uint32_t mb_load_size = 0;
>>          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);
>> +            }
>>              mb_load_size = mh_load_end_addr - mh_load_addr;
>>          } else {
>> +            if (kernel_file_size < mb_kernel_text_offset) {
>> +                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;
>>          }
>> --
>> 2.13.5
>>
>
>
>
> --
> Thomas



-- 
Thomas
Re: [Qemu-devel] [PATCH] multiboot: validate multiboot header address values
Posted by P J P 6 years, 7 months ago 
+-- On Tue, 5 Sep 2017, Thomas Garnier wrote --+
| Btw, can you open a CVE for that? (and reference it in the commit).

  Done; Sent revised patch v1.

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

Patchew 2.1-devel-0870f84

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