[PATCH 4.9 19/69] x86/vdso: Ensure vdso32_enabled gets set to valid values only
From: Greg Kroah-Hartman
Date: Wed Apr 19 2017 - 11:14:23 EST
4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mathias Krause <minipli@xxxxxxxxxxxxxx>
commit c06989da39cdb10604d572c8c7ea8c8c97f3c483 upstream.
vdso_enabled can be set to arbitrary integer values via the kernel command
line 'vdso32=' parameter or via 'sysctl abi.vsyscall32'.
load_vdso32() only maps VDSO if vdso_enabled == 1, but ARCH_DLINFO_IA32
merily checks for vdso_enabled != 0. As a consequence the AT_SYSINFO_EHDR
auxiliary vector for the VDSO_ENTRY is emitted with a NULL pointer which
causes a segfault when the application tries to use the VDSO.
Restrict the valid arguments on the command line and the sysctl to 0 and 1.
Fixes: b0b49f2673f0 ("x86, vdso: Remove compat vdso support")
Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1491424561-7187-1-git-send-email-minipli@xxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20170410151723.518412863@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/entry/vdso/vdso32-setup.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
--- a/arch/x86/entry/vdso/vdso32-setup.c
+++ b/arch/x86/entry/vdso/vdso32-setup.c
@@ -30,8 +30,10 @@ static int __init vdso32_setup(char *s)
{
vdso32_enabled = simple_strtoul(s, NULL, 0);
- if (vdso32_enabled > 1)
+ if (vdso32_enabled > 1) {
pr_warn("vdso32 values other than 0 and 1 are no longer allowed; vdso disabled\n");
+ vdso32_enabled = 0;
+ }
return 1;
}
@@ -62,13 +64,18 @@ subsys_initcall(sysenter_setup);
/* Register vsyscall32 into the ABI table */
#include <linux/sysctl.h>
+static const int zero;
+static const int one = 1;
+
static struct ctl_table abi_table2[] = {
{
.procname = "vsyscall32",
.data = &vdso32_enabled,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = (int *)&zero,
+ .extra2 = (int *)&one,
},
{}
};