This is a note to let you know that I've just added the patch titled
x86/tls: Validate TLS entries to protect espfix
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-tls-validate-tls-entries-to-protect-espfix.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 41bdc78544b8a93a9c6814b8bbbfef966272abbe Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Date: Thu, 4 Dec 2014 16:48:16 -0800
Subject: x86/tls: Validate TLS entries to protect espfix
From: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
commit 41bdc78544b8a93a9c6814b8bbbfef966272abbe upstream.
Installing a 16-bit RW data segment into the GDT defeats espfix.
AFAICT this will not affect glibc, Wine, or dosemu at all.
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Acked-by: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Willy Tarreau <w@xxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/tls.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
--- a/arch/x86/kernel/tls.c
+++ b/arch/x86/kernel/tls.c
@@ -27,6 +27,21 @@ static int get_free_idx(void)
return -ESRCH;
}
+static bool tls_desc_okay(const struct user_desc *info)
+{
+ if (LDT_empty(info))
+ return true;
+
+ /*
+ * espfix is required for 16-bit data segments, but espfix
+ * only works for LDT segments.
+ */
+ if (!info->seg_32bit)
+ return false;
+
+ return true;
+}
+
static void set_tls_desc(struct task_struct *p, int idx,
const struct user_desc *info, int n)
{
@@ -66,6 +81,9 @@ int do_set_thread_area(struct task_struc
if (copy_from_user(&info, u_info, sizeof(info)))
return -EFAULT;
+ if (!tls_desc_okay(&info))
+ return -EINVAL;
+
if (idx == -1)
idx = info.entry_number;
@@ -192,6 +210,7 @@ int regset_tls_set(struct task_struct *t
{
struct user_desc infobuf[GDT_ENTRY_TLS_ENTRIES];
const struct user_desc *info;
+ int i;
if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
(pos % sizeof(struct user_desc)) != 0 ||
@@ -205,6 +224,10 @@ int regset_tls_set(struct task_struct *t
else
info = infobuf;
+ for (i = 0; i < count / sizeof(struct user_desc); i++)
+ if (!tls_desc_okay(info + i))
+ return -EINVAL;
+
set_tls_desc(target,
GDT_ENTRY_TLS_MIN + (pos / sizeof(struct user_desc)),
info, count / sizeof(struct user_desc));
Patches currently in stable-queue which might be from luto@xxxxxxxxxxxxxx are
queue-3.10/x86-tls-disallow-unusual-tls-segments.patch
queue-3.10/x86_64-switch_to-load-tls-descriptors-before-switching-ds-and-es.patch
queue-3.10/x86-tls-validate-tls-entries-to-protect-espfix.patch
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