From 555755ecff2669f4e020147d7d3a0aec71abb679 Mon Sep 17 00:00:00 2001 From: Serhiy Storchaka Date: Sat, 12 Jan 2019 11:20:50 +0200 Subject: [2.7] bpo-35552: Fix reading past the end in PyString_FromFormat(). (GH-11276) (GH-11534) Format character "%s" in PyString_FromFormat() no longer read memory past the limit if precision is specified. (cherry picked from commit d586ccb04f79863c819b212ec5b9d873964078e4) --- .../2018-12-21-13-29-30.bpo-35552.1DzQQc.rst | 2 ++ Objects/stringobject.c | 12 +++++++++--- 2 files changed, 11 insertions(+), 3 deletions(-) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2018-12-21-13-29-30.bpo-35552.1DzQQc.rst diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-12-21-13-29-30.bpo-35552.1DzQQc.rst b/Misc/NEWS.d/next/Core and Builtins/2018-12-21-13-29-30.bpo-35552.1DzQQc.rst new file mode 100644 index 0000000..47ff76a --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2018-12-21-13-29-30.bpo-35552.1DzQQc.rst @@ -0,0 +1,2 @@ +Format character ``%s`` in :c:func:`PyString_FromFormat` no longer read +memory past the limit if *precision* is specified. diff --git a/Objects/stringobject.c b/Objects/stringobject.c index efb0d14..c47d32f 100644 --- a/Objects/stringobject.c +++ b/Objects/stringobject.c @@ -360,9 +360,15 @@ PyString_FromFormatV(const char *format, va_list vargs) break; case 's': p = va_arg(vargs, char*); - i = strlen(p); - if (n > 0 && i > n) - i = n; + if (n <= 0) { + i = strlen(p); + } + else { + i = 0; + while (i < n && p[i]) { + i++; + } + } Py_MEMCPY(s, p, i); s += i; break; -- cgit v0.12