From 79da7bb4739f9f63178ce5146702dce6b8feafb9 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jo=C3=A3o=20Abecasis?= Date: Wed, 28 Oct 2009 14:09:04 +0100 Subject: Don't try to mmap past EOF On Mac OS, mmap would succeed, returning a valid pointer, but trying to read from it would result in a SIGBUS. By adding this check we commit to a safe cross-platform behavior users can depend on. Reviewed-by: Thiago Macieira --- src/corelib/io/qfsfileengine_unix.cpp | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/corelib/io/qfsfileengine_unix.cpp b/src/corelib/io/qfsfileengine_unix.cpp index 6af5674..7824520 100644 --- a/src/corelib/io/qfsfileengine_unix.cpp +++ b/src/corelib/io/qfsfileengine_unix.cpp @@ -1250,6 +1250,12 @@ uchar *QFSFileEnginePrivate::map(qint64 offset, qint64 size, QFile::MemoryMapFla return 0; } + // If we know the mapping will extend beyond EOF, fail early to avoid + // undefined behavior. Otherwise, let mmap have its say. + if (doStat() + && (QT_OFF_T(size) > st.st_size - QT_OFF_T(offset))) + return 0; + int access = 0; if (openMode & QIODevice::ReadOnly) access |= PROT_READ; if (openMode & QIODevice::WriteOnly) access |= PROT_WRITE; -- cgit v0.12