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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 03/22] libxc: Fix range checking in xc_dom_pfn_to_ptr etc.
* 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@xxxxxxxxxxxxx>
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
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