Commit 126cf4b9 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by openeuler-sync-bot
Browse files

x86/alternatives: Disable KASAN in apply_alternatives() 

stable inclusion
from stable-v5.10.199
commit 6788b10620ca6e98575d1e06e72a8974aad7657e
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I95AT0
CVE: CVE-2023-52504

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6788b10620ca6e98575d1e06e72a8974aad7657e



--------------------------------

commit d35652a5 upstream.

Fei has reported that KASAN triggers during apply_alternatives() on
a 5-level paging machine:

	BUG: KASAN: out-of-bounds in rcu_is_watching()
	Read of size 4 at addr ff110003ee6419a0 by task swapper/0/0
	...
	__asan_load4()
	rcu_is_watching()
	trace_hardirqs_on()
	text_poke_early()
	apply_alternatives()
	...

On machines with 5-level paging, cpu_feature_enabled(X86_FEATURE_LA57)
gets patched. It includes KASAN code, where KASAN_SHADOW_START depends on
__VIRTUAL_MASK_SHIFT, which is defined with cpu_feature_enabled().

KASAN gets confused when apply_alternatives() patches the
KASAN_SHADOW_START users. A test patch that makes KASAN_SHADOW_START
static, by replacing __VIRTUAL_MASK_SHIFT with 56, works around the issue.

Fix it for real by disabling KASAN while the kernel is patching alternatives.

[ mingo: updated the changelog ]

Fixes: 6657fca0 ("x86/mm: Allow to boot without LA57 if CONFIG_X86_5LEVEL=y")
Reported-by: default avatarFei Yang <fei.yang@intel.com>
Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20231012100424.1456-1-kirill.shutemov@linux.intel.com


Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
(cherry picked from commit d02f1abb)
parent 62da3e4a

arch/x86/kernel/alternative.c

+13 −0
Original line number Diff line number Diff line
@@ -424,6 +424,17 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start, 
	u8 insn_buff[MAX_PATCH_LEN];



	DPRINTK("alt table %px, -> %px", start, end);



	/*

	 * In the case CONFIG_X86_5LEVEL=y, KASAN_SHADOW_START is defined using

	 * cpu_feature_enabled(X86_FEATURE_LA57) and is therefore patched here.

	 * During the process, KASAN becomes confused seeing partial LA57

	 * conversion and triggers a false-positive out-of-bound report.

	 *

	 * Disable KASAN until the patching is complete.

	 */

	kasan_disable_current();



	/*

	 * The scan order should be from start to end. A later scanned

	 * alternative code can overwrite previously scanned alternative code.
@@ -491,6 +502,8 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start, 
next:

		optimize_nops(instr, a->instrlen);

	}



	kasan_enable_current();

}



#if defined(CONFIG_RETPOLINE) && defined(CONFIG_STACK_VALIDATION)