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: <20191211152643.23056-43-sashal@kernel.org>
Date:   Wed, 11 Dec 2019 10:26:07 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Gustavo L. F. Walbon" <gwalbon@...ux.ibm.com>,
        "Mauro S . M . Rodrigues" <maurosr@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH AUTOSEL 4.19 43/79] powerpc/security: Fix wrong message when RFI Flush is disable

From: "Gustavo L. F. Walbon" <gwalbon@...ux.ibm.com>

[ Upstream commit 4e706af3cd8e1d0503c25332b30cad33c97ed442 ]

The issue was showing "Mitigation" message via sysfs whatever the
state of "RFI Flush", but it should show "Vulnerable" when it is
disabled.

If you have "L1D private" feature enabled and not "RFI Flush" you are
vulnerable to meltdown attacks.

"RFI Flush" is the key feature to mitigate the meltdown whatever the
"L1D private" state.

SEC_FTR_L1D_THREAD_PRIV is a feature for Power9 only.

So the message should be as the truth table shows:

  CPU | L1D private | RFI Flush |                sysfs
  ----|-------------|-----------|-------------------------------------
   P9 |    False    |   False   | Vulnerable
   P9 |    False    |   True    | Mitigation: RFI Flush
   P9 |    True     |   False   | Vulnerable: L1D private per thread
   P9 |    True     |   True    | Mitigation: RFI Flush, L1D private per thread
   P8 |    False    |   False   | Vulnerable
   P8 |    False    |   True    | Mitigation: RFI Flush

Output before this fix:
  # cat /sys/devices/system/cpu/vulnerabilities/meltdown
  Mitigation: RFI Flush, L1D private per thread
  # echo 0 > /sys/kernel/debug/powerpc/rfi_flush
  # cat /sys/devices/system/cpu/vulnerabilities/meltdown
  Mitigation: L1D private per thread

Output after fix:
  # cat /sys/devices/system/cpu/vulnerabilities/meltdown
  Mitigation: RFI Flush, L1D private per thread
  # echo 0 > /sys/kernel/debug/powerpc/rfi_flush
  # cat /sys/devices/system/cpu/vulnerabilities/meltdown
  Vulnerable: L1D private per thread

Signed-off-by: Gustavo L. F. Walbon <gwalbon@...ux.ibm.com>
Signed-off-by: Mauro S. M. Rodrigues <maurosr@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20190502210907.42375-1-gwalbon@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/kernel/security.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index a4354c4f6bc50..6a3dde9587ccb 100644
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -134,26 +134,22 @@ ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, cha
 
 	thread_priv = security_ftr_enabled(SEC_FTR_L1D_THREAD_PRIV);
 
-	if (rfi_flush || thread_priv) {
+	if (rfi_flush) {
 		struct seq_buf s;
 		seq_buf_init(&s, buf, PAGE_SIZE - 1);
 
-		seq_buf_printf(&s, "Mitigation: ");
-
-		if (rfi_flush)
-			seq_buf_printf(&s, "RFI Flush");
-
-		if (rfi_flush && thread_priv)
-			seq_buf_printf(&s, ", ");
-
+		seq_buf_printf(&s, "Mitigation: RFI Flush");
 		if (thread_priv)
-			seq_buf_printf(&s, "L1D private per thread");
+			seq_buf_printf(&s, ", L1D private per thread");
 
 		seq_buf_printf(&s, "\n");
 
 		return s.len;
 	}
 
+	if (thread_priv)
+		return sprintf(buf, "Vulnerable: L1D private per thread\n");
+
 	if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 	    !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 		return sprintf(buf, "Not affected\n");
-- 
2.20.1

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ