linux-kernel - [patch -mm] mm, doc: cleanup and clarify munmap behavior for hugetlb memory fix

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.10.1504021547330.15536@chino.kir.corp.google.com>
Date:	Thu, 2 Apr 2015 15:50:15 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Hugh Dickins <hughd@...gle.com>, Jonathan Corbet <corbet@....net>,
	Davide Libenzi <davidel@...ilserver.org>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Shuah Khan <shuahkh@....samsung.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Joern Engel <joern@...fs.org>,
	Jianguo Wu <wujianguo@...wei.com>,
	Eric B Munson <emunson@...mai.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: [patch -mm] mm, doc: cleanup and clarify munmap behavior for hugetlb
 memory fix

Don't only specify munmap(2) behavior with respect the hugetlb memory, all 
other syscalls get naturally aligned to the native page size of the 
processor.  Rather, pick out munmap(2) as a specific example.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 Documentation/vm/hugetlbpage.txt | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt
index 1270fb1..030977f 100644
--- a/Documentation/vm/hugetlbpage.txt
+++ b/Documentation/vm/hugetlbpage.txt
@@ -313,8 +313,11 @@ into /proc/sys/vm/hugetlb_shm_group.  It is possible for same or different
 applications to use any combination of mmaps and shm* calls, though the mount of
 filesystem will be required for using mmap calls without MAP_HUGETLB.
 
-When using munmap(2) to unmap hugetlb memory, the length specified must be
-hugepage aligned, otherwise it will fail with errno set to EINVAL.
+Syscalls that operate on memory backed by hugetlb pages only have their lengths
+aligned to the native page size of the processor; they will normally fail with
+errno set to EINVAL or exclude hugetlb pages that extend beyond the length if
+not hugepage aligned.  For example, munmap(2) will fail if memory is backed by
+a hugetlb page and the length is smaller than the hugepage size.
 
 
 Examples
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/