From: Andy Lutomirski <luto@xxxxxxxxxxxxxx> 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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@xxxxxxxxxxxxxx> Cc: torvalds@xxxxxxxxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/72a059de55e86ad5e2935c80aa91880ddf19d07c.1421954363.git.luto@xxxxxxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- arch/x86/include/asm/desc.h | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h index b90e5dfeee46..9210eebd079e 100644 --- a/arch/x86/include/asm/desc.h +++ b/arch/x86/include/asm/desc.h @@ -251,7 +251,8 @@ 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 && \ @@ -261,12 +262,6 @@ 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); -- 2.2.2 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html