This is a note to let you know that I've just added the patch titled
sysctl: enable strict writes
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sysctl-enable-strict-writes.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 41662f5cc55335807d39404371cfcbb1909304c4 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@xxxxxxxxxxxx>
Date: Wed, 20 Jan 2016 15:00:45 -0800
Subject: sysctl: enable strict writes
From: Kees Cook <keescook@xxxxxxxxxxxx>
commit 41662f5cc55335807d39404371cfcbb1909304c4 upstream.
SYSCTL_WRITES_WARN was added in commit f4aacea2f5d1 ("sysctl: allow for
strict write position handling"), and released in v3.16 in August of
2014. Since then I can find only 1 instance of non-zero offset
writing[1], and it was fixed immediately in CRIU[2]. As such, it
appears safe to flip this to the strict state now.
[1] https://www.google.com/search?q="when%20file%20position%20was%20not%200";
[2] http://lists.openvz.org/pipermail/criu/2015-April/019819.html
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/sysctl/kernel.txt | 15 +++++++--------
kernel/sysctl.c | 2 +-
2 files changed, 8 insertions(+), 9 deletions(-)
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -810,14 +810,13 @@ via the /proc/sys interface:
Each write syscall must fully contain the sysctl value to be
written, and multiple writes on the same sysctl file descriptor
will rewrite the sysctl value, regardless of file position.
- 0 - (default) Same behavior as above, but warn about processes that
- perform writes to a sysctl file descriptor when the file position
- is not 0.
- 1 - Respect file position when writing sysctl strings. Multiple writes
- will append to the sysctl value buffer. Anything past the max length
- of the sysctl value buffer will be ignored. Writes to numeric sysctl
- entries must always be at file position 0 and the value must be
- fully contained in the buffer sent in the write syscall.
+ 0 - Same behavior as above, but warn about processes that perform writes
+ to a sysctl file descriptor when the file position is not 0.
+ 1 - (default) Respect file position when writing sysctl strings. Multiple
+ writes will append to the sysctl value buffer. Anything past the max
+ length of the sysctl value buffer will be ignored. Writes to numeric
+ sysctl entries must always be at file position 0 and the value must
+ be fully contained in the buffer sent in the write syscall.
==============================================================
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -174,7 +174,7 @@ extern int no_unaligned_warning;
#define SYSCTL_WRITES_WARN 0
#define SYSCTL_WRITES_STRICT 1
-static int sysctl_writes_strict = SYSCTL_WRITES_WARN;
+static int sysctl_writes_strict = SYSCTL_WRITES_STRICT;
static int proc_do_cad_pid(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
Patches currently in stable-queue which might be from keescook@xxxxxxxxxxxx are
queue-4.4/sysctl-enable-strict-writes.patch