[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH 2/2] libfdt: fix undefined behaviour in _fdt_splice()



Hi Jan,

On 13/03/2020 07:35, Jan Beulich wrote:
Along the lines of commit d0b3ab0a0f46 ("libfdt: Fix undefined behaviour
in fdt_offset_ptr()"), _fdt_splice() similarly may not use pointer
arithmetic to do overflow checks.

[upstream commit 73d6e9ecb4179b510408bc526240f829262df361]
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,


--- a/xen/common/libfdt/fdt_rw.c
+++ b/xen/common/libfdt/fdt_rw.c
@@ -87,7 +87,7 @@ static int _fdt_rw_check_header(void *fd
                        return err; \
        }
-static inline int _fdt_data_size(void *fdt)
+static inline unsigned int _fdt_data_size(void *fdt)
  {
        return fdt_off_dt_strings(fdt) + fdt_size_dt_strings(fdt);
  }
@@ -95,13 +95,14 @@ static inline int _fdt_data_size(void *f
  static int _fdt_splice(void *fdt, void *splicepoint, int oldlen, int newlen)
  {
        char *p = splicepoint;
-       char *end = (char *)fdt + _fdt_data_size(fdt);
+       unsigned int dsize = _fdt_data_size(fdt);
+       size_t soff = p - (char *)fdt;
- if (((p + oldlen) < p) || ((p + oldlen) > end))
+       if (oldlen < 0 || soff + oldlen < soff || soff + oldlen > dsize)
                return -FDT_ERR_BADOFFSET;
-       if ((end - oldlen + newlen) > ((char *)fdt + fdt_totalsize(fdt)))
+       if (dsize - oldlen + newlen > fdt_totalsize(fdt))
                return -FDT_ERR_NOSPACE;
-       memmove(p + newlen, p + oldlen, end - p - oldlen);
+       memmove(p + newlen, p + oldlen, ((char *)fdt + dsize) - (p + oldlen));
        return 0;
  }

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.