package/utils/busybox/patches/005-backport-CVE-2021-28831.patch

   1 From f25d254dfd4243698c31a4f3153d4ac72aa9e9bd Mon Sep 17 00:00:00 2001
   2 From: Samuel Sapalski <samuel.sapalski@nokia.com>
   3 Date: Wed, 3 Mar 2021 16:31:22 +0100
   4 Subject: decompress_gunzip: Fix DoS if gzip is corrupt
   5
   6 On certain corrupt gzip files, huft_build will set the error bit on
   7 the result pointer. If afterwards abort_unzip is called huft_free
   8 might run into a segmentation fault or an invalid pointer to
   9 free(p).
  10
  11 In order to mitigate this, we check in huft_free if the error bit
  12 is set and clear it before the linked list is freed.
  13
  14 Signed-off-by: Samuel Sapalski <samuel.sapalski@nokia.com>
  15 Signed-off-by: Peter Kaestle <peter.kaestle@nokia.com>
  16 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
  17 ---
  18  archival/libarchive/decompress_gunzip.c | 12 ++++++++++--
  19  1 file changed, 10 insertions(+), 2 deletions(-)
  20
  21 --- a/archival/libarchive/decompress_gunzip.c
  22 +++ b/archival/libarchive/decompress_gunzip.c
  23 @@ -220,10 +220,20 @@ static const uint8_t border[] ALIGN1 = {
  24   * each table.
  25   * t: table to free
  26   */
  27 +#define BAD_HUFT(p) ((uintptr_t)(p) & 1)
  28 +#define ERR_RET     ((huft_t*)(uintptr_t)1)
  29  static void huft_free(huft_t *p)
  30  {
  31         huft_t *q;
  32
  33 +       /*
  34 +        * If 'p' has the error bit set we have to clear it, otherwise we might run
  35 +        * into a segmentation fault or an invalid pointer to free(p)
  36 +        */
  37 +       if (BAD_HUFT(p)) {
  38 +               p = (huft_t*)((uintptr_t)(p) ^ (uintptr_t)(ERR_RET));
  39 +       }
  40 +
  41         /* Go through linked list, freeing from the malloced (t[-1]) address. */
  42         while (p) {
  43                 q = (--p)->v.t;
  44 @@ -289,8 +299,6 @@ static unsigned fill_bitbuffer(STATE_PAR
  45   * or a valid pointer to a Huffman table, ORed with 0x1 if incompete table
  46   * is given: "fixed inflate" decoder feeds us such data.
  47   */
  48 -#define BAD_HUFT(p) ((uintptr_t)(p) & 1)
  49 -#define ERR_RET     ((huft_t*)(uintptr_t)1)
  50  static huft_t* huft_build(const unsigned *b, const unsigned n,
  51                         const unsigned s, const struct cp_ext *cp_ext,
  52                         unsigned *m)