linux-kernel - [PATCH] uts: Don't randomize "struct uts

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Date:   Fri,  6 Jul 2018 19:07:30 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     keescook@...omium.org
Cc:     linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: [PATCH] uts: Don't randomize "struct uts_namespace".

I noticed that makedumpfile utility is failing to check kernel version, for
it depends on offset of "struct uts_namespace"->name being sizeof(int).

----------
int
check_release(void)
{
	unsigned long utsname;

	/*
	 * Get the kernel version.
	 */
	if (SYMBOL(system_utsname) != NOT_FOUND_SYMBOL) {
		utsname = SYMBOL(system_utsname);
	} else if (SYMBOL(init_uts_ns) != NOT_FOUND_SYMBOL) {
		utsname = SYMBOL(init_uts_ns) + sizeof(int);
	} else {
		ERRMSG("Can't get the symbol of system_utsname.\n");
		return FALSE;
	}
	if (!readmem(VADDR, utsname, &info->system_utsname,
					sizeof(struct utsname))) {
		ERRMSG("Can't get the address of system_utsname.\n");
		return FALSE;
	}
----------

Since there is no way to tell the offset to userspace, let's not randomize
"struct uts_namespace".

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Fixes: 3859a271a003aba0 ("randstruct: Mark various structs for randomization")
Cc: stable <stable@...r.kernel.org> # v4.13+
---
 include/linux/utsname.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index 44429d9..85c206f 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -27,7 +27,7 @@ struct uts_namespace {
 	struct user_namespace *user_ns;
 	struct ucounts *ucounts;
 	struct ns_common ns;
-} __randomize_layout;
+};
 extern struct uts_namespace init_uts_ns;
 
 #ifdef CONFIG_UTS_NS
-- 
1.8.3.1