From: Lin Feng <linf@wangsu.com>
Date: Thu, 31 Dec 2020 22:04:41 +0000 (+0000)
Subject: sysctl.c: fix underflow value setting risk in vm_table
X-Git-Tag: howlett/maple_spf/20210104~98
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=6a8b645fc104a97a96d02a276a22c1353ee38709;p=users%2Fjedix%2Flinux-maple.git

sysctl.c: fix underflow value setting risk in vm_table

Apart from subsystem specific .proc_handler handler, all ctl_tables with
extra1 and extra2 members set should use proc_dointvec_minmax instead of
proc_dointvec, or the limit set in extra* never work and potentially echo
underflow values(negative numbers) is likely make system unstable.

Especially vfs_cache_pressure and zone_reclaim_mode, -1 is apparently not
a valid value, but we can set to them.  And then kernel may crash.

# echo -1 > /proc/sys/vm/vfs_cache_pressure

Link: https://lkml.kernel.org/r/20201223105535.2875-1-linf@wangsu.com
Signed-off-by: Lin Feng <linf@wangsu.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c9fbdd848138..62fbd09b5dc1 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2962,7 +2962,7 @@ static struct ctl_table vm_table[] = {
 		.data		= &block_dump,
 		.maxlen		= sizeof(block_dump),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ZERO,
 	},
 	{
@@ -2970,7 +2970,7 @@ static struct ctl_table vm_table[] = {
 		.data		= &sysctl_vfs_cache_pressure,
 		.maxlen		= sizeof(sysctl_vfs_cache_pressure),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ZERO,
 	},
 #if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \
@@ -2980,7 +2980,7 @@ static struct ctl_table vm_table[] = {
 		.data		= &sysctl_legacy_va_layout,
 		.maxlen		= sizeof(sysctl_legacy_va_layout),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ZERO,
 	},
 #endif
@@ -2990,7 +2990,7 @@ static struct ctl_table vm_table[] = {
 		.data		= &node_reclaim_mode,
 		.maxlen		= sizeof(node_reclaim_mode),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ZERO,
 	},
 	{