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From:   Mark-PK Tsai <mark-pk.tsai@mediatek.com>
To:     Steven Rostedt <rostedt@goodmis.org>
CC:     Ingo Molnar <mingo@redhat.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-mediatek@lists.infradead.org>, <mark-pk.tsai@mediatek.com>,
        <yj.chiang@mediatek.com>
Subject: [PATCH] arm64: ftrace: don't dereference a probably invalid address
Date:   Mon, 7 Jun 2021 11:23:30 +0800
Message-ID: <20210607032329.28671-1-mark-pk.tsai@mediatek.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Address in __mcount_loc may be invalid if somthing goes wrong.
On our arm64 platform, the bug in recordmcount make kernel
crash in ftrace_init().

https://lore.kernel.org/lkml/20210607023839.26387-1-mark-pk.tsai@mediatek.com/

Return -EFAULT if we are dealing with out-of-range condition
to prevent dereference the invalid address in ftrace_bug(),
then the kernel can disable ftrace safely for problematic
__mcount_loc.

Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
---
 arch/arm64/kernel/ftrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index b5d3ddaf69d9..98bec8445a58 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -201,7 +201,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 			preempt_enable();
 
 			if (WARN_ON(!mod))
-				return -EINVAL;
+				return -EFAULT;
 		}
 
 		/*
-- 
2.18.0