linux-kernel - [PATCH 3.12 60/88] x86/amd_nb: Fix boot crash on non-AMD systems

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Date:	Thu, 14 Jul 2016 10:15:52 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Borislav Petkov <bp@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 60/88] x86/amd_nb: Fix boot crash on non-AMD systems

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

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

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: Jiri Slaby <jslaby@...e.cz>
---
 arch/x86/kernel/amd_nb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index 6523534671b6..29957e8e2fc5 100644
--- 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)
-- 
2.9.1