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From: Ian Jackson <ian.jackson@eu.citrix.com>
To: xen-devel@lists.xensource.com
Cc: andrew.cooper3@citrix.com, mattjd@gmail.com,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	security@xen.org
Subject: [PATCH 03/22] libxc: Fix range checking in xc_dom_pfn_to_ptr etc.
Date: Tue, 11 Jun 2013 19:20:46 +0100	[thread overview]
Message-ID: <1370974865-19554-4-git-send-email-ian.jackson@eu.citrix.com> (raw)
In-Reply-To: <1370974865-19554-1-git-send-email-ian.jackson@eu.citrix.com>

* Ensure that xc_dom_pfn_to_ptr (when called with count==0) does not
  return a previously-allocated block which is entirely before the
  requested pfn (!)

* Provide a version of xc_dom_pfn_to_ptr, xc_dom_pfn_to_ptr_retcount,
  which provides the length of the mapped region via an out parameter.

* Change xc_dom_vaddr_to_ptr to always provide the length of the
  mapped region and change the call site in xc_dom_binloader.c to
  check it.  The call site in xc_dom_load_elf_symtab will be corrected
  in a forthcoming patch, and for now ignores the returned length.

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

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

v5: This patch is new in v5 of the series.
---
 tools/libxc/xc_dom.h           |   16 +++++++++++++---
 tools/libxc/xc_dom_binloader.c |   11 ++++++++++-
 tools/libxc/xc_dom_core.c      |   13 +++++++++++++
 tools/libxc/xc_dom_elfloader.c |    3 ++-
 4 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/tools/libxc/xc_dom.h b/tools/libxc/xc_dom.h
index 316c5cb..ad6fdd4 100644
--- a/tools/libxc/xc_dom.h
+++ b/tools/libxc/xc_dom.h
@@ -291,6 +291,8 @@ int xc_dom_alloc_segment(struct xc_dom_image *dom,
 
 void *xc_dom_pfn_to_ptr(struct xc_dom_image *dom, xen_pfn_t first,
                         xen_pfn_t count);
+void *xc_dom_pfn_to_ptr_retcount(struct xc_dom_image *dom, xen_pfn_t first,
+                                 xen_pfn_t count, xen_pfn_t *count_out);
 void xc_dom_unmap_one(struct xc_dom_image *dom, xen_pfn_t pfn);
 void xc_dom_unmap_all(struct xc_dom_image *dom);
 
@@ -318,13 +320,21 @@ static inline void *xc_dom_seg_to_ptr(struct xc_dom_image *dom,
 }
 
 static inline void *xc_dom_vaddr_to_ptr(struct xc_dom_image *dom,
-                                        xen_vaddr_t vaddr)
+                                        xen_vaddr_t vaddr,
+                                        size_t *safe_region_out)
 {
     unsigned int page_size = XC_DOM_PAGE_SIZE(dom);
     xen_pfn_t page = (vaddr - dom->parms.virt_base) / page_size;
     unsigned int offset = (vaddr - dom->parms.virt_base) % page_size;
-    void *ptr = xc_dom_pfn_to_ptr(dom, page, 0);
-    return (ptr ? (ptr + offset) : NULL);
+    xen_pfn_t safe_region_count;
+    void *ptr;
+
+    *safe_region_out = 0;
+    ptr = xc_dom_pfn_to_ptr_retcount(dom, page, 0, &safe_region_count);
+    if ( ptr == NULL )
+        return ptr;
+    *safe_region_out = (safe_region_count << XC_DOM_PAGE_SHIFT(dom)) - offset;
+    return ptr;
 }
 
 static inline xen_pfn_t xc_dom_p2m_host(struct xc_dom_image *dom, xen_pfn_t pfn)
diff --git a/tools/libxc/xc_dom_binloader.c b/tools/libxc/xc_dom_binloader.c
index c14727c..d2de04c 100644
--- a/tools/libxc/xc_dom_binloader.c
+++ b/tools/libxc/xc_dom_binloader.c
@@ -249,6 +249,7 @@ static int xc_dom_load_bin_kernel(struct xc_dom_image *dom)
     char *image = dom->kernel_blob;
     char *dest;
     size_t image_size = dom->kernel_size;
+    size_t dest_size;
     uint32_t start_addr;
     uint32_t load_end_addr;
     uint32_t bss_end_addr;
@@ -272,7 +273,15 @@ static int xc_dom_load_bin_kernel(struct xc_dom_image *dom)
     DOMPRINTF("  text_size: 0x%" PRIx32 "", text_size);
     DOMPRINTF("  bss_size:  0x%" PRIx32 "", bss_size);
 
-    dest = xc_dom_vaddr_to_ptr(dom, dom->kernel_seg.vstart);
+    dest = xc_dom_vaddr_to_ptr(dom, dom->kernel_seg.vstart, &dest_size);
+
+    if ( dest_size < text_size ||
+         dest_size - text_size < bss_size )
+    {
+        DOMPRINTF("%s: mapped region is too small for image", __FUNCTION__);
+        return -EINVAL;
+    }
+
     memcpy(dest, image + skip, text_size);
     memset(dest + text_size, 0, bss_size);
 
diff --git a/tools/libxc/xc_dom_core.c b/tools/libxc/xc_dom_core.c
index b92e4a9..cf96bfa 100644
--- a/tools/libxc/xc_dom_core.c
+++ b/tools/libxc/xc_dom_core.c
@@ -351,11 +351,20 @@ int xc_dom_try_gunzip(struct xc_dom_image *dom, void **blob, size_t * size)
 void *xc_dom_pfn_to_ptr(struct xc_dom_image *dom, xen_pfn_t pfn,
                         xen_pfn_t count)
 {
+    xen_pfn_t count_out_dummy;
+    return xc_dom_pfn_to_ptr_retcount(dom, pfn, count, &count_out_dummy);
+}
+
+void *xc_dom_pfn_to_ptr_retcount(struct xc_dom_image *dom, xen_pfn_t pfn,
+                                 xen_pfn_t count, xen_pfn_t *count_out)
+{
     struct xc_dom_phys *phys;
     xen_pfn_t offset;
     unsigned int page_shift = XC_DOM_PAGE_SHIFT(dom);
     char *mode = "unset";
 
+    *count_out = 0;
+
     offset = pfn - dom->rambase_pfn;
     if ( offset > dom->total_pages || /* multiple checks to avoid overflows */
          count > dom->total_pages ||
@@ -386,6 +395,7 @@ void *xc_dom_pfn_to_ptr(struct xc_dom_image *dom, xen_pfn_t pfn,
                           phys->count);
                 return NULL;
             }
+            *count_out = count;
         }
         else
         {
@@ -393,6 +403,9 @@ void *xc_dom_pfn_to_ptr(struct xc_dom_image *dom, xen_pfn_t pfn,
                just hand out a pointer to it */
             if ( pfn < phys->first )
                 continue;
+            if ( pfn >= phys->first + phys->count )
+                continue;
+            *count_out = phys->count - (pfn - phys->first);
         }
         return phys->ptr + ((pfn - phys->first) << page_shift);
     }
diff --git a/tools/libxc/xc_dom_elfloader.c b/tools/libxc/xc_dom_elfloader.c
index 6583859..bc92302 100644
--- a/tools/libxc/xc_dom_elfloader.c
+++ b/tools/libxc/xc_dom_elfloader.c
@@ -128,10 +128,11 @@ static int xc_dom_load_elf_symtab(struct xc_dom_image *dom,
 
     if ( load )
     {
+        size_t allow_size; /* will be used in a forthcoming XSA-55 patch */
         if ( !dom->bsd_symtab_start )
             return 0;
         size = dom->kernel_seg.vend - dom->bsd_symtab_start;
-        hdr  = xc_dom_vaddr_to_ptr(dom, dom->bsd_symtab_start);
+        hdr  = xc_dom_vaddr_to_ptr(dom, dom->bsd_symtab_start, &allow_size);
         *(int *)hdr = size - sizeof(int);
     }
     else
-- 
1.7.2.5

  parent reply	other threads:[~2013-06-11 18:20 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-11 18:20 [PATCH v7 00/22] XSA55 libelf fixes for unstable Ian Jackson
2013-06-11 18:20 ` [PATCH 01/22] libelf: abolish libelf-relocate.c Ian Jackson
2013-06-11 18:20 ` [PATCH 02/22] libxc: introduce xc_dom_seg_to_ptr_pages Ian Jackson
2013-06-11 18:44   ` Andrew Cooper
2013-06-11 18:20 ` Ian Jackson [this message]
2013-06-11 19:01   ` [PATCH 03/22] libxc: Fix range checking in xc_dom_pfn_to_ptr etc Andrew Cooper
2013-06-11 18:20 ` [PATCH 04/22] libelf: add `struct elf_binary*' parameter to elf_load_image Ian Jackson
2013-06-11 18:20 ` [PATCH 05/22] libelf: abolish elf_sval and elf_access_signed Ian Jackson
2013-06-11 18:20 ` [PATCH 06/22] libelf: move include of <asm/guest_access.h> to top of file Ian Jackson
2013-06-11 18:20 ` [PATCH 07/22] libelf/xc_dom_load_elf_symtab: Do not use "syms" uninitialised Ian Jackson
2013-06-11 18:20 ` [PATCH 08/22] libelf: introduce macros for memory access and pointer handling Ian Jackson
2013-06-11 18:20 ` [PATCH 09/22] tools/xcutils/readnotes: adjust print_l1_mfn_valid_note Ian Jackson
2013-06-11 18:20 ` [PATCH 10/22] libelf: check nul-terminated strings properly Ian Jackson
2013-06-11 19:14   ` Andrew Cooper
2013-06-11 18:20 ` [PATCH 11/22] libelf: check all pointer accesses Ian Jackson
2013-06-11 19:19   ` Andrew Cooper
2013-06-11 18:20 ` [PATCH 12/22] libelf: Check pointer references in elf_is_elfbinary Ian Jackson
2013-06-11 19:03   ` Andrew Cooper
2013-06-11 18:20 ` [PATCH 13/22] libelf: Make all callers call elf_check_broken Ian Jackson
2013-06-11 18:20 ` [PATCH 14/22] libelf: use C99 bool for booleans Ian Jackson
2013-06-11 19:04   ` Andrew Cooper
2013-06-11 18:20 ` [PATCH 15/22] libelf: use only unsigned integers Ian Jackson
2013-06-11 19:22   ` Andrew Cooper
2013-06-11 18:20 ` [PATCH 16/22] libelf: check loops for running away Ian Jackson
2013-06-11 19:28   ` Andrew Cooper
2013-06-11 18:21 ` [PATCH 17/22] libelf: abolish obsolete macros Ian Jackson
2013-06-11 18:21 ` [PATCH 18/22] libxc: Add range checking to xc_dom_binloader Ian Jackson
2013-06-11 19:11   ` Andrew Cooper
2013-06-11 18:21 ` [PATCH 19/22] libxc: check failure of xc_dom_*_to_ptr, xc_map_foreign_range Ian Jackson
2013-06-11 19:10   ` Andrew Cooper
2013-06-11 18:21 ` [PATCH 20/22] libxc: check return values from malloc Ian Jackson
2013-06-11 19:05   ` Andrew Cooper
2013-06-11 18:21 ` [PATCH 21/22] libxc: range checks in xc_dom_p2m_host and _guest Ian Jackson
2013-06-11 19:06   ` Andrew Cooper
2013-06-12 16:02   ` George Dunlap
2013-06-12 16:06     ` Ian Jackson
2013-06-12 16:08       ` George Dunlap
2013-06-12 18:26       ` Tim Deegan
2013-06-11 18:21 ` [PATCH 22/22] libxc: check blob size before proceeding in xc_dom_check_gzip Ian Jackson
2013-06-11 19:08   ` Andrew Cooper
2013-06-11 19:30 ` [PATCH v7 00/22] XSA55 libelf fixes for unstable Andrew Cooper
2013-06-12 13:45   ` Ian Jackson
2013-06-12 14:02     ` Ian Jackson
2013-06-12 14:19     ` Andrew Cooper
  -- strict thread matches above, loose matches on Subject: below --
2013-06-11 18:22 [PATCH v7 00/22] XSA55 libelf fixes for Xen 4.2 Ian Jackson
2013-06-11 18:22 ` [PATCH 03/22] libxc: Fix range checking in xc_dom_pfn_to_ptr etc Ian Jackson
2013-06-07 18:35 [PATCH v6 00/22] XSA55 libelf fixes for Xen 4.2 Ian Jackson
2013-06-07 18:35 ` [PATCH 03/22] libxc: Fix range checking in xc_dom_pfn_to_ptr etc Ian Jackson
2013-06-07 18:27 [PATCH v6 00/22] XSA55 libelf fixes for unstable Ian Jackson
2013-06-07 18:27 ` [PATCH 03/22] libxc: Fix range checking in xc_dom_pfn_to_ptr etc Ian Jackson
2013-06-10 15:46   ` Andrew Cooper
2013-06-10 15:48     ` Ian Jackson
2013-06-10 15:53       ` Andrew Cooper
2013-06-10 15:54         ` Ian Jackson

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