Commit e872267b authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Thomas Gleixner
Browse files

jump_table: Move entries into ro_after_init region 



The __jump_table sections emitted into the core kernel and into
each module consist of statically initialized references into
other parts of the code, and with the exception of entries that
point into init code, which are defused at post-init time, these
data structures are never modified.

So let's move them into the ro_after_init section, to prevent them
from being corrupted inadvertently by buggy code, or deliberately
by an attacker.

Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarJessica Yu <jeyu@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Link: https://lkml.kernel.org/r/20180919065144.25010-9-ard.biesheuvel@linaro.org
parent 19483677

arch/s390/kernel/vmlinux.lds.S

+1 −0
Original line number Diff line number Diff line
@@ -66,6 +66,7 @@ SECTIONS 
		 *(.data..ro_after_init)

	}

	EXCEPTION_TABLE(16)

	JUMP_TABLE_DATA

	. = ALIGN(PAGE_SIZE);

	__end_ro_after_init = .;

include/asm-generic/vmlinux.lds.h

+7 −4
Original line number Diff line number Diff line
@@ -254,10 +254,6 @@ 
	*(__tracepoints)						\

	/* implement dynamic printk debug */				\

	. = ALIGN(8);							\

	__start___jump_table = .;					\

	KEEP(*(__jump_table))                                           \

	__stop___jump_table = .;					\

	. = ALIGN(8);							\

	__start___verbose = .;						\

	KEEP(*(__verbose))                                              \

	__stop___verbose = .;						\
@@ -300,6 +296,12 @@ 
	. = __start_init_task + THREAD_SIZE;				\

	__end_init_task = .;



#define JUMP_TABLE_DATA							\

	. = ALIGN(8);							\

	__start___jump_table = .;					\

	KEEP(*(__jump_table))						\

	__stop___jump_table = .;



/*

 * Allow architectures to handle ro_after_init data on their

 * own by defining an empty RO_AFTER_INIT_DATA.
@@ -308,6 +310,7 @@ 
#define RO_AFTER_INIT_DATA						\

	__start_ro_after_init = .;					\

	*(.data..ro_after_init)						\

	JUMP_TABLE_DATA							\

	__end_ro_after_init = .;

#endif

kernel/module.c

+9 −0
Original line number Diff line number Diff line
@@ -3315,6 +3315,15 @@ static struct module *layout_and_allocate(struct load_info *info, int flags) 
	 * Note: ro_after_init sections also have SHF_{WRITE,ALLOC} set.

	 */

	ndx = find_sec(info, ".data..ro_after_init");

	if (ndx)

		info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT;

	/*

	 * Mark the __jump_table section as ro_after_init as well: these data

	 * structures are never modified, with the exception of entries that

	 * refer to code in the __init section, which are annotated as such

	 * at module load time.

	 */

	ndx = find_sec(info, "__jump_table");

	if (ndx)

		info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT;

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