From: Mathias Krause 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: Roland McGrath Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1491424561-7187-1-git-send-email-minipli@googlemail.com Signed-off-by: Thomas Gleixner --- 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 +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, }, {} };