linux-kernel - [PATCH 3.16 260/305] x86/amd_nb: Fix boot crash on non-AMD systems

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Message-ID: <lsq.1471110171.460699755@decadent.org.uk>
Date:	Sat, 13 Aug 2016 18:42:51 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...nel.org>, "Borislav Petkov" <bp@...e.de>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Peter Zijlstra" <peterz@...radead.org>
Subject: [PATCH 3.16 260/305] x86/amd_nb: Fix boot crash on non-AMD systems

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Borislav Petkov <bp@...e.de>

commit 1ead852dd88779eda12cb09cc894a03d9abfe1ec upstream.

Fix boot crash that triggers if this driver is built into a kernel and
run on non-AMD systems.

AMD northbridges users call amd_cache_northbridges() and it returns
a negative value to signal that we weren't able to cache/detect any
northbridges on the system.

At least, it should do so as all its callers expect it to do so. But it
does return a negative value only when kmalloc() fails.

Fix it to return -ENODEV if there are no NBs cached as otherwise, amd_nb
users like amd64_edac, for example, which relies on it to know whether
it should load or not, gets loaded on systems like Intel Xeons where it
shouldn't.

Reported-and-tested-by: Tony Battersby <tonyb@...ernetics.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1466097230-5333-2-git-send-email-bp@alien8.de
Link: https://lkml.kernel.org/r/5761BEB0.9000807@cybernetics.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kernel/amd_nb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -69,8 +69,8 @@ int amd_cache_northbridges(void)
 	while ((misc = next_northbridge(misc, amd_nb_misc_ids)) != NULL)
 		i++;

-	if (i == 0)
-		return 0;
+	if (!i)
+		return -ENODEV;

 	nb = kzalloc(i * sizeof(struct amd_northbridge), GFP_KERNEL);
 	if (!nb)