linux-kernel - [RFC PATCH v2 6/8] arm64: Check the return PC of every stack frame

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Message-Id: <20210315165800.5948-7-madvenka@linux.microsoft.com>
Date:   Mon, 15 Mar 2021 11:57:58 -0500
From:   madvenka@...ux.microsoft.com
To:     broonie@...nel.org, mark.rutland@....com, jpoimboe@...hat.com,
        jthierry@...hat.com, catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        madvenka@...ux.microsoft.com
Subject: [RFC PATCH v2 6/8] arm64: Check the return PC of every stack frame

From: "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>

If a function encountered in a stack trace is not a valid kernel text
address, the stack trace is considered unreliable. Mark the stack trace
as not reliable.

Signed-off-by: Madhavan T. Venkataraman <madvenka@...ux.microsoft.com>
---
 arch/arm64/kernel/stacktrace.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 594806a0c225..358aae3906d7 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -101,6 +101,16 @@ static void check_if_reliable(unsigned long fp, struct stackframe *frame,
 		}
 	}
 #endif
+
+	/*
+	 * A NULL or invalid return address probably means there's some
+	 * generated code which __kernel_text_address() doesn't know about.
+	 * Mark the stack trace as not reliable.
+	 */
+	if (!__kernel_text_address(frame->pc)) {
+		frame->reliable = false;
+		return;
+	}
 }
 
 /*
-- 
2.25.1