From e320a8c7802eb54f80693db03bb2a201580875e7 Mon Sep 17 00:00:00 2001 From: Elliott Hughes Date: Thu, 25 Jul 2013 10:15:07 -0700 Subject: [PATCH] Avoid sign extension of the mmap offset. off_t is signed to support seeking backwards, but that's a liability when using off_t to represent a subset of a file. Change-Id: I2a3615166eb16212347eb47f1242e3bfb93c2022 --- libc/bionic/mmap.cpp | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/libc/bionic/mmap.cpp b/libc/bionic/mmap.cpp index 864dea20c..febc459fa 100644 --- a/libc/bionic/mmap.cpp +++ b/libc/bionic/mmap.cpp @@ -37,13 +37,14 @@ extern "C" void* __mmap2(void*, size_t, int, int, int, size_t); #define MMAP2_SHIFT 12 // 2**12 == 4096 -void* mmap(void* addr, size_t size, int prot, int flags, int fd, long offset) { +void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) { if (offset & ((1UL << MMAP2_SHIFT)-1)) { errno = EINVAL; return MAP_FAILED; } - void* result = __mmap2(addr, size, prot, flags, fd, offset >> MMAP2_SHIFT); + size_t unsigned_offset = static_cast(offset); // To avoid sign extension. + void* result = __mmap2(addr, size, prot, flags, fd, unsigned_offset >> MMAP2_SHIFT); if (result != MAP_FAILED && (flags & (MAP_PRIVATE | MAP_ANONYMOUS)) != 0) { ErrnoRestorer errno_restorer;