Eric Lee / smarc-ti-linux-kernel

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Commit e3b3b6d580b073a5fbf9b74495a88eb9f69bb23c

Authored by Andy Lutomirski
Committed by Greg Kroah-Hartman
1 parent f84d9d8d9b

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Showing 1 changed file with 2 additions and 7 deletions Side-by-side Diff

arch/x86/include/asm/desc.h
Diff comments   View file @ e3b3b6d
... ... @@ -251,7 +251,8 @@
251 251 gdt[GDT_ENTRY_TLS_MIN + i] = t->tls_array[i];
252 252 }
253 253  
254   -#define _LDT_empty(info) \
  254 +/* This intentionally ignores lm, since 32-bit apps don't have that field. */
  255 +#define LDT_empty(info) \
255 256 ((info)->base_addr == 0 && \
256 257 (info)->limit == 0 && \
257 258 (info)->contents == 0 && \
... ... @@ -260,12 +261,6 @@
260 261 (info)->limit_in_pages == 0 && \
261 262 (info)->seg_not_present == 1 && \
262 263 (info)->useable == 0)
263   -
264   -#ifdef CONFIG_X86_64
265   -#define LDT_empty(info) (_LDT_empty(info) && ((info)->lm == 0))
266   -#else
267   -#define LDT_empty(info) (_LDT_empty(info))
268   -#endif
269 264  
270 265 static inline void clear_LDT(void)
271 266 {