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From: Tony Luck <tony.luck@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: "Tony Luck" <tony.luck@intel.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	"Andy Lutomirski" <luto@kernel.org>,
	"Aili Yao" <yaoaili@kingsoft.com>,
	"HORIGUCHI NAOYA( 堀口 直也)" <naoya.horiguchi@nec.com>
Subject: [PATCH 1/4] x86/mce: Fix copyin code to return -EFAULT on machine check.
Date: Thu, 25 Mar 2021 17:02:32 -0700	[thread overview]
Message-ID: <20210326000235.370514-2-tony.luck@intel.com> (raw)
In-Reply-To: <20210326000235.370514-1-tony.luck@intel.com>

When copy from user fails due to a machine check on poison reading
user data it should return an error code.

---

Separate patch just now, but likely needs to be combined with patches
to iteration code for bisection safety.
---
 arch/x86/lib/copy_user_64.S | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index 77b9b2a3b5c8..2987118c541a 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -14,6 +14,7 @@
 #include <asm/alternative-asm.h>
 #include <asm/asm.h>
 #include <asm/smap.h>
+#include <asm/errno.h>
 #include <asm/export.h>
 #include <asm/trapnr.h>
 
@@ -237,18 +238,21 @@ SYM_CODE_START_LOCAL(.Lcopy_user_handle_tail)
 	cmp $X86_TRAP_MC,%eax		/* check if X86_TRAP_MC */
 	je 3f
 1:	rep movsb
-2:	mov %ecx,%eax
+	mov %ecx,%eax
+	ASM_CLAC
+	ret
+
+2:
+	cmp $X86_TRAP_MC,%eax
+	je 3f
+	mov %ecx,%eax
 	ASM_CLAC
 	ret
 
 	/*
-	 * Return zero to pretend that this copy succeeded. This
-	 * is counter-intuitive, but needed to prevent the code
-	 * in lib/iov_iter.c from retrying and running back into
-	 * the poison cache line again. The machine check handler
-	 * will ensure that a SIGBUS is sent to the task.
+	 * Return -EFAULT for the machine check cases
 	 */
-3:	xorl %eax,%eax
+3:	movl $-EFAULT,%eax
 	ASM_CLAC
 	ret
 
-- 
2.29.2



  reply	other threads:[~2021-03-26  0:02 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-26  0:02 [RFC 0/4] Fix machine check recovery for copy_from_user Tony Luck
2021-03-26  0:02 ` Tony Luck [this message]
2021-04-06 19:24   ` [PATCH 1/4] x86/mce: Fix copyin code to return -EFAULT on machine check Borislav Petkov
2021-03-26  0:02 ` [PATCH 2/4] mce/iter: Check for copyin failure & return error up stack Tony Luck
2021-03-26  0:02 ` [PATCH 3/4] mce/copyin: fix to not SIGBUS when copying from user hits poison Tony Luck
2021-04-07 21:18   ` Borislav Petkov
2021-04-07 21:43     ` Luck, Tony
2021-04-08  8:49       ` Borislav Petkov
2021-04-08 17:08         ` Luck, Tony
2021-04-13 10:07           ` Borislav Petkov
2021-04-13 16:13             ` Luck, Tony
2021-04-14 13:05               ` Borislav Petkov
2021-03-26  0:02 ` [PATCH 4/4] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-04-08 13:36   ` Borislav Petkov
2021-04-08 16:06     ` Luck, Tony
2021-04-08  2:13 ` [RFC 0/4] Fix machine check recovery for copy_from_user Aili Yao
2021-04-08 14:39   ` Luck, Tony
2021-04-09  6:49     ` Aili Yao

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