4.14-stable review patch. If anyone has any objections, please let me know.
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From: Michael Ellerman mpe@ellerman.id.au
commit 92edf8df0ff2ae86cc632eeca0e651fd8431d40d upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/kernel/security.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-)
--- a/arch/powerpc/kernel/security.c +++ b/arch/powerpc/kernel/security.c @@ -189,29 +189,22 @@ ssize_t cpu_show_spectre_v2(struct devic 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 {