[Xen-changelog] [qemu-xen master] multiboot: validate multiboot header address values

[patchbot@xxxxxxx]

commit fca5f37fe9016cfea90c31d3e35e4154ef1a7f28
Author:     Prasad J Pandit <pjp@xxxxxxxxxxxxxxxxx>
AuthorDate: Thu Sep 7 12:02:56 2017 +0530
Commit:     Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CommitDate: Fri Sep 22 18:11:49 2017 -0500

    multiboot: validate multiboot header address values
    
    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.
    
    This is CVE-2017-14167.
    
    Reported-by: Thomas Garnier <thgarnie@xxxxxxxxxx>
    Signed-off-by: Prasad J Pandit <pjp@xxxxxxxxxxxxxxxxx>
    Message-Id: <20170907063256.7418-1-ppandit@xxxxxxxxxx>
    Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    (cherry picked from commit ed4f86e8b6eff8e600c69adee68c7cd34dd2cccb)
    Signed-off-by: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
---
 hw/i386/multiboot.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
index f13e231..22688d3 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;
         }
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog