The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 92edf8df0ff2ae86cc632eeca0e651fd8431d40d Mon Sep 17 00:00:00 2001
From: Michael Ellerman mpe@ellerman.id.au Date: Thu, 21 Mar 2019 15:24:33 +1100 Subject: [PATCH] powerpc/security: Fix spectre_v2 reporting
When I updated the spectre_v2 reporting to handle software count cache flush I got the logic wrong when there's no software count cache enabled at all.
The result is that on systems with the software count cache flush disabled we print:
Mitigation: Indirect branch cache disabled, Software count cache flush
Which correctly indicates that the count cache is disabled, but incorrectly says the software count cache flush is enabled.
The root of the problem is that we are trying to handle all combinations of options. But we know now that we only expect to see the software count cache flush enabled if the other options are false.
So split the two cases, which simplifies the logic and fixes the bug. We were also missing a space before "(hardware accelerated)".
The result is we see one of:
Mitigation: Indirect branch serialisation (kernel only) Mitigation: Indirect branch cache disabled Mitigation: Software count cache flush Mitigation: Software count cache flush (hardware accelerated)
Fixes: ee13cb249fab ("powerpc/64s: Add support for software count cache flush") Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Michael Ellerman mpe@ellerman.id.au Reviewed-by: Michael Neuling mikey@neuling.org Reviewed-by: Diana Craciun diana.craciun@nxp.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au
diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c index 9b8631533e02..b33bafb8fcea 100644 --- a/arch/powerpc/kernel/security.c +++ b/arch/powerpc/kernel/security.c @@ -190,29 +190,22 @@ ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, c bcs = security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED); ccd = security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED);
- if (bcs || ccd || count_cache_flush_type != COUNT_CACHE_FLUSH_NONE) { - bool comma = false; + if (bcs || ccd) { seq_buf_printf(&s, "Mitigation: ");
- if (bcs) { + if (bcs) seq_buf_printf(&s, "Indirect branch serialisation (kernel only)"); - comma = true; - }
- if (ccd) { - if (comma) - seq_buf_printf(&s, ", "); - seq_buf_printf(&s, "Indirect branch cache disabled"); - comma = true; - } - - if (comma) + if (bcs && ccd) seq_buf_printf(&s, ", ");
- seq_buf_printf(&s, "Software count cache flush"); + if (ccd) + seq_buf_printf(&s, "Indirect branch cache disabled"); + } else if (count_cache_flush_type != COUNT_CACHE_FLUSH_NONE) { + seq_buf_printf(&s, "Mitigation: Software count cache flush");
if (count_cache_flush_type == COUNT_CACHE_FLUSH_HW) - seq_buf_printf(&s, "(hardware accelerated)"); + seq_buf_printf(&s, " (hardware accelerated)"); } else if (btb_flush_enabled) { seq_buf_printf(&s, "Mitigation: Branch predictor state flush"); } else {