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Commit 2cfe0d30 authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds
Browse files

task_struct: only use anon struct under randstruct plugin 

The original intent for always adding the anonymous struct in
task_struct was to make sure we had compiler coverage.

However, this caused pathological padding of 40 bytes at the start of
task_struct.  Instead, move the anonymous struct to being only used when
struct layout randomization is enabled.

Link: http://lkml.kernel.org/r/20180327213609.GA2964@beast


Fixes: 29e48ce8 ("task_struct: Allow randomized")
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Reported-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d4ef8d3f

include/linux/compiler-clang.h

+0 −3
Original line number Original line Diff line number Diff line
@@ -17,9 +17,6 @@ 
 */

 */

#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)

#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)





#define randomized_struct_fields_start	struct {

#define randomized_struct_fields_end	};



/* all clang versions usable with the kernel support KASAN ABI version 5 */

/* all clang versions usable with the kernel support KASAN ABI version 5 */

#define KASAN_ABI_VERSION 5

#define KASAN_ABI_VERSION 5

include/linux/compiler-gcc.h

+3 −9
Original line number Original line Diff line number Diff line
@@ -242,6 +242,9 @@ 
#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)

#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)

#define __randomize_layout __attribute__((randomize_layout))

#define __randomize_layout __attribute__((randomize_layout))

#define __no_randomize_layout __attribute__((no_randomize_layout))

#define __no_randomize_layout __attribute__((no_randomize_layout))

/* This anon struct can add padding, so only enable it under randstruct. */

#define randomized_struct_fields_start	struct {

#define randomized_struct_fields_end	} __randomize_layout;

#endif

#endif





#endif /* GCC_VERSION >= 40500 */

#endif /* GCC_VERSION >= 40500 */
@@ -256,15 +259,6 @@ 
 */

 */

#define __visible	__attribute__((externally_visible))

#define __visible	__attribute__((externally_visible))





/*

 * RANDSTRUCT_PLUGIN wants to use an anonymous struct, but it is only

 * possible since GCC 4.6. To provide as much build testing coverage

 * as possible, this is used for all GCC 4.6+ builds, and not just on

 * RANDSTRUCT_PLUGIN builds.

 */

#define randomized_struct_fields_start	struct {

#define randomized_struct_fields_end	} __randomize_layout;



#endif /* GCC_VERSION >= 40600 */

#endif /* GCC_VERSION >= 40600 */