Fix #8530: Prevent stringlib fastsearch from reading beyond the front of an array.
diff --git a/Misc/NEWS b/Misc/NEWS
index 9f3d80a..7aba37d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
Core and Builtins
-----------------
+- Issue #8530: Prevent stringlib fastsearch from reading beyond the front
+ of an array.
+
- Issue #5319: Print an error if flushing stdout fails at interpreter
shutdown.
diff --git a/Objects/stringlib/fastsearch.h b/Objects/stringlib/fastsearch.h
index 7525951..e231c58 100644
--- a/Objects/stringlib/fastsearch.h
+++ b/Objects/stringlib/fastsearch.h
@@ -140,13 +140,13 @@
/* got a match! */
return i;
/* miss: check if previous character is part of pattern */
- if (!STRINGLIB_BLOOM(mask, s[i-1]))
+ if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1]))
i = i - m;
else
i = i - skip;
} else {
/* skip: check if previous character is part of pattern */
- if (!STRINGLIB_BLOOM(mask, s[i-1]))
+ if (i > 0 && !STRINGLIB_BLOOM(mask, s[i-1]))
i = i - m;
}
}