blob: 4edeb722beb41abdd473514d9439fd293bcd5a14 [file] [log] [blame]
From 8c2974258c4d58e6ebe0a9e8af02a1ba9ee84d0b Mon Sep 17 00:00:00 2001
From: "Gustavo L. F. Walbon" <gwalbon@linux.ibm.com>
Date: Thu, 2 May 2019 18:09:07 -0300
Subject: [PATCH] powerpc/security: Fix wrong message when RFI Flush is disable
commit 4e706af3cd8e1d0503c25332b30cad33c97ed442 upstream.
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@linux.ibm.com>
Signed-off-by: Mauro S. M. Rodrigues <maurosr@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190502210907.42375-1-gwalbon@linux.ibm.com
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index 298a2e3ad6f4..d341b464f23c 100644
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -142,26 +142,22 @@ 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");
--
2.7.4