Add underflow check in JIT.

git-svn-id: svn://vcs.exim.org/pcre2/code/trunk@1167 6239d852-aaf2-0410-a92c-79f79f948069

2 files changed, 9 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 62cd860..948c147 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -146,6 +146,9 @@ compile-time performance improvement).
 31. Installed a .gitignore file on a user's suggestion. When using the svn
 repository with git (through git svn) this helps keep it tidy.
 
+32. Add underflow check in JIT which may occure when the value of subject
+string pointer is close to 0.
+
 
 Version 10.33 16-April-2019
 ---------------------------
diff --git a/src/pcre2_jit_compile.c b/src/pcre2_jit_compile.c
index 8cbd8f9..79a27fd 100644
--- a/src/pcre2_jit_compile.c
+++ b/src/pcre2_jit_compile.c
@@ -5793,12 +5793,16 @@ if (common->match_end_ptr != 0)
   {
   OP1(SLJIT_MOV, TMP1, 0, SLJIT_MEM1(SLJIT_SP), common->match_end_ptr);
   OP1(SLJIT_MOV, TMP3, 0, STR_END, 0);
-  OP2(SLJIT_SUB, STR_END, 0, STR_END, 0, SLJIT_IMM, IN_UCHARS(max));
+  OP2(SLJIT_SUB | SLJIT_SET_LESS, STR_END, 0, STR_END, 0, SLJIT_IMM, IN_UCHARS(max));
+  add_jump(compiler, &common->failed_match, JUMP(SLJIT_LESS));
   OP2(SLJIT_SUB | SLJIT_SET_GREATER, SLJIT_UNUSED, 0, STR_END, 0, TMP1, 0);
   CMOV(SLJIT_GREATER, STR_END, TMP1, 0);
   }
 else
-  OP2(SLJIT_SUB, STR_END, 0, STR_END, 0, SLJIT_IMM, IN_UCHARS(max));
+  {
+  OP2(SLJIT_SUB | SLJIT_SET_LESS, STR_END, 0, STR_END, 0, SLJIT_IMM, IN_UCHARS(max));
+  add_jump(compiler, &common->failed_match, JUMP(SLJIT_LESS));
+  }
 
 SLJIT_ASSERT(range_right >= 0);