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authorAndy Lutomirski <luto@amacapital.net>2015-01-22 11:27:58 -0800
committerBen Hutchings <ben@decadent.org.uk>2015-02-20 00:49:39 +0000
commitf62570cbdcb6dd53d0e2361488f9ea2c4cf17ec9 (patch)
tree2630aac9ef065f08383a11682bd59863da67f4a8 /arch/x86/include
parentcea62dbdc110e3e8d5db8fb9eebebf01587830b8 (diff)
x86, tls, ldt: Stop checking lm in LDT_empty
commit e30ab185c490e9a9381385529e0fd32f0a399495 upstream. 32-bit programs don't have an lm bit in their ABI, so they can't reliably cause LDT_empty to return true without resorting to memset. They shouldn't need to do this. This should fix a longstanding, if minor, issue in all 64-bit kernels as well as a potential regression in the TLS hardening code. Fixes: 41bdc78544b8 x86/tls: Validate TLS entries to protect espfix Signed-off-by: Andy Lutomirski <luto@amacapital.net> Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/72a059de55e86ad5e2935c80aa91880ddf19d07c.1421954363.git.luto@amacapital.net Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch/x86/include')
-rw-r--r--arch/x86/include/asm/desc.h9
1 files changed, 2 insertions, 7 deletions
diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index 41935fadfdfc..baebc210b9d9 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -248,7 +248,8 @@ static inline void native_load_tls(struct thread_struct *t, unsigned int cpu)
gdt[GDT_ENTRY_TLS_MIN + i] = t->tls_array[i];
}
-#define _LDT_empty(info) \
+/* This intentionally ignores lm, since 32-bit apps don't have that field. */
+#define LDT_empty(info) \
((info)->base_addr == 0 && \
(info)->limit == 0 && \
(info)->contents == 0 && \
@@ -258,12 +259,6 @@ static inline void native_load_tls(struct thread_struct *t, unsigned int cpu)
(info)->seg_not_present == 1 && \
(info)->useable == 0)
-#ifdef CONFIG_X86_64
-#define LDT_empty(info) (_LDT_empty(info) && ((info)->lm == 0))
-#else
-#define LDT_empty(info) (_LDT_empty(info))
-#endif
-
static inline void clear_LDT(void)
{
set_ldt(NULL, 0);