Commit c06989da authored Apr 10, 2017 by Mathias Krause Committed by Thomas Gleixner Apr 10, 2017

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: b0b49f26 ("x86, vdso: Remove compat vdso support")
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Cc: Roland McGrath <roland@redhat.com>
Link: http://lkml.kernel.org/r/1491424561-7187-1-git-send-email-minipli@googlemail.com
Link: http://lkml.kernel.org/r/20170410151723.518412863@linutronix.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent cfac6dfa

arch/x86/entry/vdso/vdso32-setup.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -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,
		},
		{}
		};

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