libbacktrace patch RFC: check size passed to backtrace_get_view

[Ian Lance Taylor]

I agree that checking the size passed to backtrace_get_view seems like
the most reliable approach to avoid problems with large files on
32-bit systems.  How does this patch look?

Ian


2019-01-18  Ian Lance Taylor  <i...@golang.org>

PR libbacktrace/88890
* mmapio.c (backtrace_get_view): Change size parameter to
uint64_t.  Check that value fits in size_t.
* read.c (backtrace_get_view): Likewise.
* internal.h (backtrace_get_view): Update declaration.
* elf.c (elf_add): Pass shstrhdr->sh_size to backtrace_get_view.

Index: elf.c
===================================================================
--- elf.c       (revision 268078)
+++ elf.c       (working copy)
@@ -2813,7 +2813,7 @@ elf_add (struct backtrace_state *state,
   shstr_size = shstrhdr->sh_size;
   shstr_off = shstrhdr->sh_offset;
 
-  if (!backtrace_get_view (state, descriptor, shstr_off, shstr_size,
+  if (!backtrace_get_view (state, descriptor, shstr_off, shstrhdr->sh_size,
                           error_callback, data, &names_view))
     goto fail;
   names_view_valid = 1;
Index: internal.h
===================================================================
--- internal.h  (revision 268078)
+++ internal.h  (working copy)
@@ -179,7 +179,7 @@ struct backtrace_view
 /* Create a view of SIZE bytes from DESCRIPTOR at OFFSET.  Store the
    result in *VIEW.  Returns 1 on success, 0 on error.  */
 extern int backtrace_get_view (struct backtrace_state *state, int descriptor,
-                              off_t offset, size_t size,
+                              off_t offset, uint64_t size,
                               backtrace_error_callback error_callback,
                               void *data, struct backtrace_view *view);
 
Index: mmapio.c
===================================================================
--- mmapio.c    (revision 268078)
+++ mmapio.c    (working copy)
@@ -51,7 +51,7 @@ POSSIBILITY OF SUCH DAMAGE.  */
 
 int
 backtrace_get_view (struct backtrace_state *state ATTRIBUTE_UNUSED,
-                   int descriptor, off_t offset, size_t size,
+                   int descriptor, off_t offset, uint64_t size,
                    backtrace_error_callback error_callback,
                    void *data, struct backtrace_view *view)
 {
@@ -60,6 +60,12 @@ backtrace_get_view (struct backtrace_sta
   off_t pageoff;
   void *map;
 
+  if ((uint64_t) (size_t) size != size)
+    {
+      error_callback (data, "file size too large", 0);
+      return 0;
+    }
+
   pagesize = getpagesize ();
   inpage = offset % pagesize;
   pageoff = offset - inpage;
Index: read.c
===================================================================
--- read.c      (revision 268078)
+++ read.c      (working copy)
@@ -46,12 +46,18 @@ POSSIBILITY OF SUCH DAMAGE.  */
 
 int
 backtrace_get_view (struct backtrace_state *state, int descriptor,
-                   off_t offset, size_t size,
+                   off_t offset, uint64_t size,
                    backtrace_error_callback error_callback,
                    void *data, struct backtrace_view *view)
 {
   ssize_t got;
 
+  if ((uint64_t) (size_t) size != size)
+    {
+      error_callback (data, "file size too large", 0);
+      return 0;
+    }
+
   if (lseek (descriptor, offset, SEEK_SET) < 0)
     {
       error_callback (data, "lseek", errno);