linux-kernel - [PATCH 2/3] x86/perf/hw_breakpoint: Improve range breakpoint validation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <ae25d14d61f2f43b78e0a247e469f3072df7e201.1438312874.git.luto@kernel.org>
Date:	Thu, 30 Jul 2015 20:32:41 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Cc:	Brian Gerst <brgerst@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	X86 ML <x86@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 2/3] x86/perf/hw_breakpoint: Improve range breakpoint validation

Range breakpoints will do the wrong thing if the address isn't
aligned.  While we're there, add comments about why it's safe for
instruction breakpoints.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/kernel/hw_breakpoint.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index 78f3e90c5659..6f345d302cf6 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -291,8 +291,18 @@ static int arch_build_bp_info(struct perf_event *bp)
 		break;
 #endif
 	default:
+		/* AMD range breakpoint */
 		if (!is_power_of_2(bp->attr.bp_len))
 			return -EINVAL;
+		if (bp->attr.bp_addr & (bp->attr.bp_len - 1))
+			return -EINVAL;
+		/*
+		 * It's impossible to use a range breakpoint to fake out
+		 * user vs kernel detection because bp_len - 1 can't
+		 * have the high bit set.  If we ever allow range instruction
+		 * breakpoints, then we'll have to check for kprobe-blacklisted
+		 * addresses anywhere in the range.
+		 */
 		if (!cpu_has_bpext)
 			return -EOPNOTSUPP;
 		info->mask = bp->attr.bp_len - 1;
-- 
2.4.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/