path: root/app-emulation/xen-pvgrub/files/xen-4.2-CVE-2013-12to13-XSA-55.patch

From d0790bdad7496e720416b2d4a04563c4c27e7b95 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ian.jackson@eu.citrix.com>
Date: Fri, 14 Jun 2013 16:43:17 +0100
Subject: [PATCH 12/23] libelf: Check pointer references in elf_is_elfbinary

elf_is_elfbinary didn't take a length parameter and could potentially
access out of range when provided with a very short image.

We only need to check the size is enough for the actual dereference in
elf_is_elfbinary; callers are just using it to check the magic number
and do their own checks (usually via the new elf_ptrval system) before
dereferencing other parts of the header.

This is part of the fix to a security issue, XSA-55.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 tools/libxc/xc_dom_elfloader.c    |    2 +-
 xen/arch/x86/bzimage.c            |    4 ++--
 xen/common/libelf/libelf-loader.c |    2 +-
 xen/common/libelf/libelf-tools.c  |    9 ++++++---
 xen/include/xen/libelf.h          |    4 +++-
 5 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/tools/libxc/xc_dom_elfloader.c b/tools/libxc/xc_dom_elfloader.c
index b82a08c..ea45886 100644
--- a/tools/libxc/xc_dom_elfloader.c
+++ b/tools/libxc/xc_dom_elfloader.c
@@ -95,7 +95,7 @@ static int check_elf_kernel(struct xc_dom_image *dom, int verbose)
         return -EINVAL;
     }
 
-    if ( !elf_is_elfbinary(dom->kernel_blob) )
+    if ( !elf_is_elfbinary(dom->kernel_blob, dom->kernel_size) )
     {
         if ( verbose )
             xc_dom_panic(dom->xch,
diff --git a/xen/arch/x86/bzimage.c b/xen/arch/x86/bzimage.c
index 5adc223..3600dca 100644
--- a/xen/arch/x86/bzimage.c
+++ b/xen/arch/x86/bzimage.c
@@ -220,7 +220,7 @@ unsigned long __init bzimage_headroom(char *image_start,
         image_length = hdr->payload_length;
     }
 
-    if ( elf_is_elfbinary(image_start) )
+    if ( elf_is_elfbinary(image_start, image_length) )
         return 0;
 
     orig_image_len = image_length;
@@ -251,7 +251,7 @@ int __init bzimage_parse(char *image_base, char **image_start, unsigned long *im
         *image_len = hdr->payload_length;
     }
 
-    if ( elf_is_elfbinary(*image_start) )
+    if ( elf_is_elfbinary(*image_start, *image_len) )
         return 0;
 
     BUG_ON(!(image_base < *image_start));
diff --git a/xen/common/libelf/libelf-loader.c b/xen/common/libelf/libelf-loader.c
index a3310e7..f8be635 100644
--- a/xen/common/libelf/libelf-loader.c
+++ b/xen/common/libelf/libelf-loader.c
@@ -29,7 +29,7 @@ int elf_init(struct elf_binary *elf, const char *image_input, size_t size)
     ELF_HANDLE_DECL(elf_shdr) shdr;
     uint64_t i, count, section, offset;
 
-    if ( !elf_is_elfbinary(image_input) )
+    if ( !elf_is_elfbinary(image_input, size) )
     {
         elf_err(elf, "%s: not an ELF binary\n", __FUNCTION__);
         return -1;
diff --git a/xen/common/libelf/libelf-tools.c b/xen/common/libelf/libelf-tools.c
index 46ca553..744027e 100644
--- a/xen/common/libelf/libelf-tools.c
+++ b/xen/common/libelf/libelf-tools.c
@@ -332,11 +332,14 @@ ELF_HANDLE_DECL(elf_note) elf_note_next(struct elf_binary *elf, ELF_HANDLE_DECL(
 
 /* ------------------------------------------------------------------------ */
 
-int elf_is_elfbinary(const void *image)
+int elf_is_elfbinary(const void *image_start, size_t image_size)
 {
-    const Elf32_Ehdr *ehdr = image;
+    const Elf32_Ehdr *ehdr = image_start;
 
-    return IS_ELF(*ehdr); /* fixme unchecked */
+    if ( image_size < sizeof(*ehdr) )
+        return 0;
+
+    return IS_ELF(*ehdr);
 }
 
 int elf_phdr_is_loadable(struct elf_binary *elf, ELF_HANDLE_DECL(elf_phdr) phdr)
diff --git a/xen/include/xen/libelf.h b/xen/include/xen/libelf.h
index ddc3ed7..ac93858 100644
--- a/xen/include/xen/libelf.h
+++ b/xen/include/xen/libelf.h
@@ -350,7 +350,9 @@ uint64_t elf_note_numeric_array(struct elf_binary *, ELF_HANDLE_DECL(elf_note),
                                 unsigned int unitsz, unsigned int idx);
 ELF_HANDLE_DECL(elf_note) elf_note_next(struct elf_binary *elf, ELF_HANDLE_DECL(elf_note) note);
 
-int elf_is_elfbinary(const void *image);
+/* (Only) checks that the image has the right magic number. */
+int elf_is_elfbinary(const void *image_start, size_t image_size);
+
 int elf_phdr_is_loadable(struct elf_binary *elf, ELF_HANDLE_DECL(elf_phdr) phdr);
 
 /* ------------------------------------------------------------------------ */
-- 
1.7.2.5
#From a965b8f80388603d439ae2b8ee7b9b018a079f90 Mon Sep 17 00:00:00 2001
#From: Ian Jackson <ian.jackson@eu.citrix.com>
#Date: Fri, 14 Jun 2013 16:43:17 +0100
#Subject: [PATCH 13/23] libelf: Make all callers call elf_check_broken
#
#This arranges that if the new pointer reference error checking
#tripped, we actually get a message about it.  In this patch these
#messages do not change the actual return values from the various
#functions: so pointer reference errors do not prevent loading.  This
#is for fear that some existing kernels might cause the code to make
#these wild references, which would then break, which is not a good
#thing in a security patch.
#
#In xen/arch/x86/domain_build.c we have to introduce an "out" label and
#change all of the "return rc" beyond the relevant point into "goto
#out".
#
#Difference in the 4.2 series, compared to unstable:
#
#* tools/libxc/xc_hvm_build_x86.c:setup_guest and
#  xen/arch/arm/kernel.c:kernel_try_elf_prepare have different
#  error handling in 4.2 to unstable; patch adjusted accordingly.
#
#This is part of the fix to a security issue, XSA-55.
#
#Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
#
#xen-unstable version Reviewed-by: George Dunlap <george.dunlap@eu.citrix.com>
#---
# tools/libxc/xc_dom_elfloader.c |   25 +++++++++++++++++++++----
# tools/libxc/xc_hvm_build_x86.c |    5 +++++
# tools/xcutils/readnotes.c      |    3 +++
# xen/arch/arm/kernel.c          |   15 ++++++++++++++-
# xen/arch/x86/domain_build.c    |   28 +++++++++++++++++++++-------
# 5 files changed, 64 insertions(+), 12 deletions(-)
#
diff --git a/tools/libxc/xc_dom_elfloader.c b/tools/libxc/xc_dom_elfloader.c
index ea45886..4fb4da2 100644
--- a/tools/libxc/xc_dom_elfloader.c
+++ b/tools/libxc/xc_dom_elfloader.c
@@ -276,6 +276,13 @@ static int xc_dom_load_elf_symtab(struct xc_dom_image *dom,
             elf_store_field(elf, shdr, e32.sh_name, 0);
     }
 
+    if ( elf_check_broken(&syms) )
+        DOMPRINTF("%s: symbols ELF broken: %s", __FUNCTION__,
+                  elf_check_broken(&syms));
+    if ( elf_check_broken(elf) )
+        DOMPRINTF("%s: ELF broken: %s", __FUNCTION__,
+                  elf_check_broken(elf));
+
     if ( tables == 0 )
     {
         DOMPRINTF("%s: no symbol table present", __FUNCTION__);
@@ -312,19 +319,23 @@ static int xc_dom_parse_elf_kernel(struct xc_dom_image *dom)
     {
         xc_dom_panic(dom->xch, XC_INVALID_KERNEL, "%s: ELF image"
                      " has no shstrtab", __FUNCTION__);
-        return -EINVAL;
+        rc = -EINVAL;
+        goto out;
     }
 
     /* parse binary and get xen meta info */
     elf_parse_binary(elf);
     if ( (rc = elf_xen_parse(elf, &dom->parms)) != 0 )
-        return rc;
+    {
+        goto out;
+    }
 
     if ( elf_xen_feature_get(XENFEAT_dom0, dom->parms.f_required) )
     {
         xc_dom_panic(dom->xch, XC_INVALID_KERNEL, "%s: Kernel does not"
                      " support unprivileged (DomU) operation", __FUNCTION__);
-        return -EINVAL;
+        rc = -EINVAL;
+        goto out;
     }
 
     /* find kernel segment */
@@ -338,7 +349,13 @@ static int xc_dom_parse_elf_kernel(struct xc_dom_image *dom)
     DOMPRINTF("%s: %s: 0x%" PRIx64 " -> 0x%" PRIx64 "",
               __FUNCTION__, dom->guest_type,
               dom->kernel_seg.vstart, dom->kernel_seg.vend);
-    return 0;
+    rc = 0;
+out:
+    if ( elf_check_broken(elf) )
+        DOMPRINTF("%s: ELF broken: %s", __FUNCTION__,
+                  elf_check_broken(elf));
+
+    return rc;
 }
 
 static int xc_dom_load_elf_kernel(struct xc_dom_image *dom)
diff --git a/tools/libxc/xc_hvm_build_x86.c b/tools/libxc/xc_hvm_build_x86.c
index ccfd8b5..8165287 100644
--- a/tools/libxc/xc_hvm_build_x86.c
+++ b/tools/libxc/xc_hvm_build_x86.c
@@ -403,11 +403,16 @@ static int setup_guest(xc_interface *xch,
         munmap(page0, PAGE_SIZE);
     }
 
+    if ( elf_check_broken(&elf) )
+        ERROR("HVM ELF broken: %s", elf_check_broken(&elf));
+
     free(page_array);
     return 0;
 
  error_out:
     free(page_array);
+    if ( elf_check_broken(&elf) )
+        ERROR("HVM ELF broken, failing: %s", elf_check_broken(&elf));
     return -1;
 }
 
diff --git a/tools/xcutils/readnotes.c b/tools/xcutils/readnotes.c
index cfae994..d1f7a30 100644
--- a/tools/xcutils/readnotes.c
+++ b/tools/xcutils/readnotes.c
@@ -301,6 +301,9 @@ int main(int argc, char **argv)
 		printf("__xen_guest: %s\n",
                        elf_strfmt(&elf, elf_section_start(&elf, shdr)));
 
+	if (elf_check_broken(&elf))
+		printf("warning: broken ELF: %s\n", elf_check_broken(&elf));
+
 	return 0;
 }
 
diff --git a/xen/arch/arm/kernel.c b/xen/arch/arm/kernel.c
index 2d56130..dec0519 100644
--- a/xen/arch/arm/kernel.c
+++ b/xen/arch/arm/kernel.c
@@ -146,6 +146,8 @@ static int kernel_try_elf_prepare(struct kernel_info *info)
 {
     int rc;
 
+    memset(&info->elf.elf, 0, sizeof(info->elf.elf));
+
     info->kernel_order = get_order_from_bytes(KERNEL_FLASH_SIZE);
     info->kernel_img = alloc_xenheap_pages(info->kernel_order, 0);
     if ( info->kernel_img == NULL )
@@ -160,7 +162,7 @@ static int kernel_try_elf_prepare(struct kernel_info *info)
 #endif
     elf_parse_binary(&info->elf.elf);
     if ( (rc = elf_xen_parse(&info->elf.elf, &info->elf.parms)) != 0 )
-        return rc;
+        goto err;
 
     /*
      * TODO: can the ELF header be used to find the physical address
@@ -169,7 +171,18 @@ static int kernel_try_elf_prepare(struct kernel_info *info)
     info->entry = info->elf.parms.virt_entry;
     info->load = kernel_elf_load;
 
+    if ( elf_check_broken(&info->elf.elf) )
+        printk("Xen: warning: ELF kernel broken: %s\n",
+               elf_check_broken(&info->elf.elf));
+
     return 0;
+
+err:
+    if ( elf_check_broken(&info->elf.elf) )
+        printk("Xen: ELF kernel broken: %s\n",
+               elf_check_broken(&info->elf.elf));
+
+    return rc;
 }
 
 int kernel_prepare(struct kernel_info *info)
diff --git a/xen/arch/x86/domain_build.c b/xen/arch/x86/domain_build.c
index a655b21..0dbec96 100644
--- a/xen/arch/x86/domain_build.c
+++ b/xen/arch/x86/domain_build.c
@@ -374,7 +374,7 @@ int __init construct_dom0(
 #endif
     elf_parse_binary(&elf);
     if ( (rc = elf_xen_parse(&elf, &parms)) != 0 )
-        return rc;
+        goto out;
 
     /* compatibility check */
     compatible = 0;
@@ -413,14 +413,16 @@ int __init construct_dom0(
     if ( !compatible )
     {
         printk("Mismatch between Xen and DOM0 kernel\n");
-        return -EINVAL;
+        rc = -EINVAL;
+        goto out;
     }
 
     if ( parms.elf_notes[XEN_ELFNOTE_SUPPORTED_FEATURES].type != XEN_ENT_NONE &&
          !test_bit(XENFEAT_dom0, parms.f_supported) )
     {
         printk("Kernel does not support Dom0 operation\n");
-        return -EINVAL;
+        rc = -EINVAL;
+        goto out;
     }
 
 #if defined(__x86_64__)
@@ -734,7 +736,8 @@ int __init construct_dom0(
          (v_end > HYPERVISOR_COMPAT_VIRT_START(d)) )
     {
         printk("DOM0 image overlaps with Xen private area.\n");
-        return -EINVAL;
+        rc = -EINVAL;
+        goto out;
     }
 
     if ( is_pv_32on64_domain(d) )
@@ -914,7 +917,7 @@ int __init construct_dom0(
     if ( rc < 0 )
     {
         printk("Failed to load the kernel binary\n");
-        return rc;
+        goto out;
     }
     bootstrap_map(NULL);
 
@@ -925,7 +928,8 @@ int __init construct_dom0(
         {
             write_ptbase(current);
             printk("Invalid HYPERCALL_PAGE field in ELF notes.\n");
-            return -1;
+            rc = -1;
+            goto out;
         }
         hypercall_page_initialise(
             d, (void *)(unsigned long)parms.virt_hypercall);
@@ -1272,9 +1276,19 @@ int __init construct_dom0(
 
     BUG_ON(rc != 0);
 
-    iommu_dom0_init(dom0);
+    if ( elf_check_broken(&elf) )
+        printk(" Xen warning: dom0 kernel broken ELF: %s\n",
+               elf_check_broken(&elf));
 
+    iommu_dom0_init(dom0);
     return 0;
+
+out:
+    if ( elf_check_broken(&elf) )
+        printk(" Xen dom0 kernel broken ELF: %s\n",
+               elf_check_broken(&elf));
+
+    return rc;
 }
 
 /*
-- 
1.7.2.5