linux-kernel - [PATCH 5.4 19/66] x86/entry/32: Fix IRET exception

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Message-Id: <20191127202654.282045144@linuxfoundation.org>
Date:   Wed, 27 Nov 2019 21:32:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lai Jiangshan <laijs@...ux.alibaba.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>, stable@...nel.org
Subject: [PATCH 5.4 19/66] x86/entry/32: Fix IRET exception

From: Peter Zijlstra <peterz@...radead.org>

commit 40ad2199580e248dce2a2ebb722854180c334b9e upstream.

As reported by Lai, the commit 3c88c692c287 ("x86/stackframe/32:
Provide consistent pt_regs") wrecked the IRET EXTABLE entry by making
.Lirq_return not point at IRET.

Fix this by placing IRET_FRAME in RESTORE_REGS, to mirror how
FIXUP_FRAME is part of SAVE_ALL.

Fixes: 3c88c692c287 ("x86/stackframe/32: Provide consistent pt_regs")
Reported-by: Lai Jiangshan <laijs@...ux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Andy Lutomirski <luto@...nel.org>
Cc: stable@...nel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/entry/entry_32.S |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -357,6 +357,7 @@
 2:	popl	%es
 3:	popl	%fs
 	POP_GS \pop
+	IRET_FRAME
 .pushsection .fixup, "ax"
 4:	movl	$0, (%esp)
 	jmp	1b
@@ -1075,7 +1076,6 @@ restore_all:
 	/* Restore user state */
 	RESTORE_REGS pop=4			# skip orig_eax/error_code
 .Lirq_return:
-	IRET_FRAME
 	/*
 	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on IRET core serialization
 	 * when returning from IPI handler and when returning from