Patch "powerpc/security: Fix spectre_v2 reporting" has been added to the 4.19-stable tree

gregkh at gregkh at
Sat Mar 30 02:07:54 AEDT 2019

This is a note to let you know that I've just added the patch titled

    powerpc/security: Fix spectre_v2 reporting

to the 4.19-stable tree which can be found at:;a=summary

The filename of the patch is:
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at> know about it.

>From foo at baz Fri Mar 29 16:04:51 CET 2019
From: Michael Ellerman <mpe at>
Date: Fri, 29 Mar 2019 22:26:20 +1100
Subject: powerpc/security: Fix spectre_v2 reporting
To: stable at, gregkh at
Cc: linuxppc-dev at, diana.craciun at, msuchanek at, christophe.leroy at
Message-ID: <20190329112620.14489-33-mpe at>

From: Michael Ellerman <mpe at>

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 at # v4.19+
Signed-off-by: Michael Ellerman <mpe at>
Reviewed-by: Michael Neuling <mikey at>
Reviewed-by: Diana Craciun <diana.craciun at>
Signed-off-by: Michael Ellerman <mpe at>
Signed-off-by: Greg Kroah-Hartman <gregkh at>
 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 {

Patches currently in stable-queue which might be from mpe at are


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