Fix 32-bit mmap/mmap64 handling of negative offsets.
We don't actually need to worry about sign extension if we reject
negative values ourselves. Previously it was possible to come up
with negative but aligned values that we would pass to the kernel;
in the case of mmap (as opposed to mmap64) we'd incorrectly turn
those into large positive offsets.
Change-Id: I2aa583e0f892d59bb77429aea8730b72db32dcb0
diff --git a/libc/bionic/mmap.cpp b/libc/bionic/mmap.cpp
index 84a0f76..28a47cc 100644
--- a/libc/bionic/mmap.cpp
+++ b/libc/bionic/mmap.cpp
@@ -38,14 +38,12 @@
#define MMAP2_SHIFT 12 // 2**12 == 4096
void* mmap64(void* addr, size_t size, int prot, int flags, int fd, off64_t offset) {
- if (offset & ((1UL << MMAP2_SHIFT)-1)) {
+ if (offset < 0 || (offset & ((1UL << MMAP2_SHIFT)-1)) != 0) {
errno = EINVAL;
return MAP_FAILED;
}
- uint64_t unsigned_offset = static_cast<uint64_t>(offset); // To avoid sign extension.
- void* result = __mmap2(addr, size, prot, flags, fd, unsigned_offset >> MMAP2_SHIFT);
-
+ void* result = __mmap2(addr, size, prot, flags, fd, offset >> MMAP2_SHIFT);
if (result != MAP_FAILED && (flags & (MAP_PRIVATE | MAP_ANONYMOUS)) != 0) {
ErrnoRestorer errno_restorer;
madvise(result, size, MADV_MERGEABLE);
@@ -55,5 +53,5 @@
}
void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) {
- return mmap64(addr, size, prot, flags, fd, static_cast<off64_t>(offset) & 0xffffffff);
+ return mmap64(addr, size, prot, flags, fd, static_cast<off64_t>(offset));
}