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From: Waiman Long <longman@redhat.com>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jonathan Corbet <corbet@lwn.net>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-doc@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
	Matthew Wilcox <willy@infradead.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Waiman Long <longman@redhat.com>
Subject: [PATCH v6 4/8] ipc: Clamp msgmni and shmmni to the real IPCMNI limit
Date: Fri, 27 Apr 2018 17:00:34 -0400	[thread overview]
Message-ID: <1524862838-8247-5-git-send-email-longman@redhat.com> (raw)
In-Reply-To: <1524862838-8247-1-git-send-email-longman@redhat.com>

A user can write arbitrary integer values to msgmni and shmmni sysctl
parameters without getting error, but the actual limit is really
IPCMNI (32k). This can mislead users as they think they can get a
value that is not real.

Enforcing the limit by failing the sysctl parameter write, however,
can break existing user applications in case they are writing a value
greater than 32k. Instead, the range clamping flag is set to enforce
the limit without failing existing user code. Users can easily figure
out if the sysctl parameter value is out of range by either reading
back the parameter value or checking the kernel ring buffer for warning.

Signed-off-by: Waiman Long <longman@redhat.com>
---
 ipc/ipc_sysctl.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index 8ad93c2..d71f949 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -99,6 +99,7 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write,
 static int zero;
 static int one = 1;
 static int int_max = INT_MAX;
+static int ipc_mni = IPCMNI;
 
 static struct ctl_table ipc_kern_table[] = {
 	{
@@ -120,7 +121,10 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write,
 		.data		= &init_ipc_ns.shm_ctlmni,
 		.maxlen		= sizeof(init_ipc_ns.shm_ctlmni),
 		.mode		= 0644,
-		.proc_handler	= proc_ipc_dointvec,
+		.proc_handler	= proc_ipc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &ipc_mni,
+		.flags		= CTL_FLAGS_CLAMP_SIGNED_RANGE,
 	},
 	{
 		.procname	= "shm_rmid_forced",
@@ -147,7 +151,8 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write,
 		.mode		= 0644,
 		.proc_handler	= proc_ipc_dointvec_minmax,
 		.extra1		= &zero,
-		.extra2		= &int_max,
+		.extra2		= &ipc_mni,
+		.flags		= CTL_FLAGS_CLAMP_SIGNED_RANGE,
 	},
 	{
 		.procname	= "auto_msgmni",
-- 
1.8.3.1

  parent reply	other threads:[~2018-04-27 21:02 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27 21:00 [PATCH v6 0/8] ipc: Clamp *mni to the real IPCMNI limit & increase that limit Waiman Long
2018-04-27 21:00 ` [PATCH v6 1/8] sysctl: Add flags to support min/max range clamping Waiman Long
2018-04-27 21:00 ` [PATCH v6 2/8] proc/sysctl: Provide additional ctl_table.flags checks Waiman Long
2018-04-27 21:00 ` [PATCH v6 3/8] sysctl: Warn when a clamped sysctl parameter is set out of range Waiman Long
2018-04-30 22:40   ` Kees Cook
2018-05-01 13:41     ` Waiman Long
2018-04-27 21:00 ` Waiman Long [this message]
2018-04-27 21:00 ` [PATCH v6 5/8] ipc: Clamp semmni to the real IPCMNI limit Waiman Long
2018-04-27 21:00 ` [PATCH v6 6/8] test_sysctl: Add range clamping test Waiman Long
2018-04-27 21:00 ` [PATCH v6 7/8] ipc: Allow boot time extension of IPCMNI from 32k to 2M Waiman Long
2018-04-29 15:54   ` kbuild test robot
2018-04-27 21:00 ` [PATCH v6 8/8] ipc: Conserve sequence numbers in extended IPCMNI mode Waiman Long
2018-04-29 16:51   ` kbuild test robot
2018-05-02  2:18 ` [PATCH v6 0/8] ipc: Clamp *mni to the real IPCMNI limit & increase that limit Eric W. Biederman
2018-05-02 13:23   ` Waiman Long
2018-05-02 15:06     ` Eric W. Biederman
2018-05-07 19:14       ` Waiman Long

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