Linus,
Please pull the latest x86-urgent-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
x86-urgent-for-linus
# HEAD: 3fb2f4237bb452eb4e98f6a5dbd5a445b4fed9d0 x86/tls: Don't validate lm
in set_thread_area() after all
This tree contains a single TLS ABI validation fix from Andy
Lutomirski.
Thanks,
Ingo
------------------>
Andy Lutomirski (1):
x86/tls: Don't validate lm in set_thread_area() after all
arch/x86/include/uapi/asm/ldt.h | 7 +++++++
arch/x86/kernel/tls.c | 6 ------
2 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/uapi/asm/ldt.h b/arch/x86/include/uapi/asm/ldt.h
index 46727eb37bfe..6e1aaf73852a 100644
--- a/arch/x86/include/uapi/asm/ldt.h
+++ b/arch/x86/include/uapi/asm/ldt.h
@@ -28,6 +28,13 @@ struct user_desc {
unsigned int seg_not_present:1;
unsigned int useable:1;
#ifdef __x86_64__
+ /*
+ * Because this bit is not present in 32-bit user code, user
+ * programs can pass uninitialized values here. Therefore, in
+ * any context in which a user_desc comes from a 32-bit program,
+ * the kernel must act as though lm == 0, regardless of the
+ * actual value.
+ */
unsigned int lm:1;
#endif
};
diff --git a/arch/x86/kernel/tls.c b/arch/x86/kernel/tls.c
index 3e551eee87b9..4e942f31b1a7 100644
--- a/arch/x86/kernel/tls.c
+++ b/arch/x86/kernel/tls.c
@@ -55,12 +55,6 @@ static bool tls_desc_okay(const struct user_desc *info)
if (info->seg_not_present)
return false;
-#ifdef CONFIG_X86_64
- /* The L bit makes no sense for data. */
- if (info->lm)
- return false;
-#endif
-
return true;
}
--
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