[tip:x86/urgent] x86/vdso: Ensure vdso32_enabled gets set to valid values only

[tip-bot for Mathias Krause]

Commit-ID:  c06989da39cdb10604d572c8c7ea8c8c97f3c483
Gitweb: http://git.kernel.org/tip/c06989da39cdb10604d572c8c7ea8c8c97f3c483
Author: Mathias Krause 
AuthorDate: Mon, 10 Apr 2017 17:14:27 +0200
Committer:  Thomas Gleixner 
CommitDate: Mon, 10 Apr 2017 18:31:41 +0200

x86/vdso: Ensure vdso32_enabled gets set to valid values only

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 
Acked-by: Andy Lutomirski 
Cc: Peter Zijlstra 
Cc: sta...@vger.kernel.org
Cc: Roland McGrath 
Link: 
http://lkml.kernel.org/r/1491424561-7187-1-git-send-email-mini...@googlemail.com
Link: http://lkml.kernel.org/r/20170410151723.518412...@linutronix.de
Signed-off-by: Thomas Gleixner 

---
 arch/x86/entry/vdso/vdso32-setup.c | 11 +--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/vdso/vdso32-setup.c 
b/arch/x86/entry/vdso/vdso32-setup.c
index 7853b53..3f9d1a8 100644
--- 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 
 
+static const int zero;
+static const int one = 1;
+
 static struct ctl_table abi_table2[] = {
{
.procname   = "vsyscall32",
.data   = _enabled,
.maxlen = sizeof(int),
.mode   = 0644,
-   .proc_handler   = proc_dointvec
+   .proc_handler   = proc_dointvec_minmax,
+   .extra1 = (int *),
+   .extra2 = (int *),
},
{}
 };

[tip:x86/urgent] x86/vdso: Ensure vdso32_enabled gets set to valid values only

[tip-bot for Mathias Krause]

Commit-ID:  c06989da39cdb10604d572c8c7ea8c8c97f3c483
Gitweb: http://git.kernel.org/tip/c06989da39cdb10604d572c8c7ea8c8c97f3c483
Author: Mathias Krause 
AuthorDate: Mon, 10 Apr 2017 17:14:27 +0200
Committer:  Thomas Gleixner 
CommitDate: Mon, 10 Apr 2017 18:31:41 +0200

x86/vdso: Ensure vdso32_enabled gets set to valid values only

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 
Acked-by: Andy Lutomirski 
Cc: Peter Zijlstra 
Cc: sta...@vger.kernel.org
Cc: Roland McGrath 
Link: 
http://lkml.kernel.org/r/1491424561-7187-1-git-send-email-mini...@googlemail.com
Link: http://lkml.kernel.org/r/20170410151723.518412...@linutronix.de
Signed-off-by: Thomas Gleixner 

---
 arch/x86/entry/vdso/vdso32-setup.c | 11 +--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/vdso/vdso32-setup.c 
b/arch/x86/entry/vdso/vdso32-setup.c
index 7853b53..3f9d1a8 100644
--- 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 
 
+static const int zero;
+static const int one = 1;
+
 static struct ctl_table abi_table2[] = {
{
.procname   = "vsyscall32",
.data   = _enabled,
.maxlen = sizeof(int),
.mode   = 0644,
-   .proc_handler   = proc_dointvec
+   .proc_handler   = proc_dointvec_minmax,
+   .extra1 = (int *),
+   .extra2 = (int *),
},
{}
 };