From c7d93b761413834e0ac39f5fc648565a2843121f Mon Sep 17 00:00:00 2001 From: Mark Dickinson Date: Sun, 25 Sep 2011 15:34:32 +0100 Subject: Issue #1621: Fix undefined behaviour from signed overflow in datetime module hashes, array and list iterations, and get_integer (stringlib/string_format.h) --- Objects/stringlib/string_format.h | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) (limited to 'Objects/stringlib/string_format.h') diff --git a/Objects/stringlib/string_format.h b/Objects/stringlib/string_format.h index 6c7adcb01ed..d992b6f53c3 100644 --- a/Objects/stringlib/string_format.h +++ b/Objects/stringlib/string_format.h @@ -209,19 +209,17 @@ get_integer(const SubString *str) if (digitval < 0) return -1; /* - This trick was copied from old Unicode format code. It's cute, - but would really suck on an old machine with a slow divide - implementation. Fortunately, in the normal case we do not - expect too many digits. + Detect possible overflow before it happens: + + accumulator * 10 + digitval > PY_SSIZE_T_MAX if and only if + accumulator > (PY_SSIZE_T_MAX - digitval) / 10. */ - oldaccumulator = accumulator; - accumulator *= 10; - if ((accumulator+10)/10 != oldaccumulator+1) { + if (accumulator > (PY_SSIZE_T_MAX - digitval) / 10) { PyErr_Format(PyExc_ValueError, "Too many decimal digits in format string"); return -1; } - accumulator += digitval; + accumulator = accumulator * 10 + digitval; } return accumulator; } -- cgit v1.2.3