[PATCH 1/2] regex: fix buffer overrun in regexp matcher

[Paul Eggert]

* lib/regexec.c (extend_buffers): Add parameter min_len.
(check_matching): Pass minimum needed length.
(clean_state_log_if_needed): Likewise.
(get_subexp): Likewise.
---
 ChangeLog     |  8 ++++++++
 lib/regexec.c | 16 +++++++++-------
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 9145f2f..ab95829 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2013-01-29  Andreas Schwab  <sch...@suse.de>
+
+       regex: fix buffer overrun in regexp matcher
+       * lib/regexec.c (extend_buffers): Add parameter min_len.
+       (check_matching): Pass minimum needed length.
+       (clean_state_log_if_needed): Likewise.
+       (get_subexp): Likewise.
+
 2013-01-28  Pádraig Brady  <p...@draigbrady.com>
 
        mountlist: don't consider "devtmpfs" as dummy
diff --git a/lib/regexec.c b/lib/regexec.c
index 41ac4d4..1bd1640 100644
--- a/lib/regexec.c
+++ b/lib/regexec.c
@@ -199,7 +199,7 @@ static Idx group_nodes_into_DFAstates (const re_dfa_t *dfa,
 static bool check_node_accept (const re_match_context_t *mctx,
                               const re_token_t *node, Idx idx)
      internal_function;
-static reg_errcode_t extend_buffers (re_match_context_t *mctx)
+static reg_errcode_t extend_buffers (re_match_context_t *mctx, int min_len)
      internal_function;
 
 /* Entry point for POSIX code.  */
@@ -1176,7 +1176,7 @@ check_matching (re_match_context_t *mctx, bool 
fl_longest_match,
          || (BE (next_char_idx >= mctx->input.valid_len, 0)
              && mctx->input.valid_len < mctx->input.len))
        {
-         err = extend_buffers (mctx);
+         err = extend_buffers (mctx, next_char_idx + 1);
          if (BE (err != REG_NOERROR, 0))
            {
              assert (err == REG_ESPACE);
@@ -1756,7 +1756,7 @@ clean_state_log_if_needed (re_match_context_t *mctx, Idx 
next_state_log_idx)
          && mctx->input.valid_len < mctx->input.len))
     {
       reg_errcode_t err;
-      err = extend_buffers (mctx);
+      err = extend_buffers (mctx, next_state_log_idx + 1);
       if (BE (err != REG_NOERROR, 0))
        return err;
     }
@@ -2813,7 +2813,7 @@ get_subexp (re_match_context_t *mctx, Idx bkref_node, Idx 
bkref_str_idx)
                  if (bkref_str_off >= mctx->input.len)
                    break;
 
-                 err = extend_buffers (mctx);
+                 err = extend_buffers (mctx, bkref_str_off + 1);
                  if (BE (err != REG_NOERROR, 0))
                    return err;
 
@@ -4128,7 +4128,7 @@ check_node_accept (const re_match_context_t *mctx, const 
re_token_t *node,
 
 static reg_errcode_t
 internal_function __attribute_warn_unused_result__
-extend_buffers (re_match_context_t *mctx)
+extend_buffers (re_match_context_t *mctx, int min_len)
 {
   reg_errcode_t ret;
   re_string_t *pstr = &mctx->input;
@@ -4138,8 +4138,10 @@ extend_buffers (re_match_context_t *mctx)
           <= pstr->bufs_len, 0))
     return REG_ESPACE;
 
-  /* Double the lengths of the buffers.  */
-  ret = re_string_realloc_buffers (pstr, MIN (pstr->len, pstr->bufs_len * 2));
+  /* Double the lengths of the buffers, but allocate at least MIN_LEN.  */
+  ret = re_string_realloc_buffers (pstr,
+                                  MAX (min_len,
+                                       MIN (pstr->len, pstr->bufs_len * 2)));
   if (BE (ret != REG_NOERROR, 0))
     return ret;
 
-- 
1.7.11.7