posix: Fix generic p{read,write}v buffer allocation (BZ#22457)

As described in BZ#22457 an interpose malloc can free an invalid
pointer for fallback preadv implementation.  Fortunately this is
just and issue on microblaze-linux-gnu running kernels older than
3.15.  This patch fixes it by calling mmap/unmap instead of
posix_memalign/ free.

Checked on microblaze-linux-gnu check with run-built-tests=no and
by using the sysdeps/posix implementation on x86_64-linux-gnu (just
for sanity test where it shown no regression).

	[BZ #22457]
	* sysdeps/posix/preadv_common.c (PREADV): Use mmap/munmap instead of
	posix_memalign/free.
	* sysdeps/posix/pwritev_common.c (PWRITEV): Likewise.

1 files changed, 7 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index e60983a50f..6791c51308 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2017-11-24  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+
+	[BZ #22457]
+	* sysdeps/posix/preadv_common.c (PREADV): Use mmap/munmap instead of
+	posix_memalign/free.
+	* sysdeps/posix/pwritev_common.c (PWRITEV): Likewise.
+
 2017-11-22  Mike FABIAN  <mfabian@redhat.com>
 
 	[BZ #22469]