lkml.org 
[lkml]   [2014]   [Oct]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:x86/vdso] x86/vdso: Make the PER_CPU segment 32 bits
Commit-ID:  287e013108a104e459e675432cf20087feab2b67
Gitweb: http://git.kernel.org/tip/287e013108a104e459e675432cf20087feab2b67
Author: Andy Lutomirski <luto@amacapital.net>
AuthorDate: Tue, 23 Sep 2014 10:50:55 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 28 Oct 2014 11:22:12 +0100

x86/vdso: Make the PER_CPU segment 32 bits

IMO users ought not to be able to use 16-bit segments without
using modify_ldt. Fortunately, it's impossible to break
espfix64 by loading the PER_CPU segment into SS because it's
PER_CPU is marked read-only and SS cannot contain an RO segment,
but marking PER_CPU as 32-bit is less fragile.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/179f490d659307873eefd09206bebd417e2ab5ad.1411494540.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/vdso/vma.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
index 0c799746..32ca60c 100644
--- a/arch/x86/vdso/vma.c
+++ b/arch/x86/vdso/vma.c
@@ -268,6 +268,7 @@ static void vsyscall_set_cpu(int cpu)
.dpl = 3, /* Visible to user code */
.s = 1, /* Not a system segment */
.p = 1, /* Present */
+ .d = 1, /* 32-bit */
};

write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);

\
 
 \ /
  Last update: 2014-10-28 12:41    [W:0.098 / U:0.472 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site