linux-kernel - [PATCH 2/3] perf/x86: Tighten up the kernel

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Message-Id: <20160915132944.10331-3-alexander.shishkin@linux.intel.com>
Date:   Thu, 15 Sep 2016 16:29:43 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        vince@...ter.net, eranian@...gle.com,
        Arnaldo Carvalho de Melo <acme@...radead.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        stable@...r.kernel.org#4.7
Subject: [PATCH 2/3] perf/x86: Tighten up the kernel_ip() check

The kernel_ip() filter is used mostly by the DS/LBR code to look at the
branch addresses, but Intel PT also uses it to validate the address
filter offsets for kernel addresses, for which it is not sufficient:
supplying something in bits 64:48 that's not a sign extension of the lower
address bits (like 0xf00d000000000000) throws a #GP.

In the interest of improving everybody's kernel address checks, this
patch adds address validation to kernel_ip().

Cc: stable@...r.kernel.org # 4.7
Reported-by: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
 arch/x86/events/perf_event.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 5874d8de1f..88fb389356 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -783,7 +783,7 @@ static inline bool kernel_ip(unsigned long ip)
 #ifdef CONFIG_X86_32
 	return ip > PAGE_OFFSET;
 #else
-	return (long)ip < 0;
+	return (long)ip < 0 && virt_addr_valid(ip);
 #endif
 }
 
-- 
2.9.3