linux-kernel - [PATCH 3.10 115/180] x86/amd_nb: Fix boot crash on non-AMD systems

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Message-Id: <1471793510-13022-116-git-send-email-w@1wt.eu>
Date:   Sun, 21 Aug 2016 17:30:45 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     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>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 115/180] x86/amd_nb: Fix boot crash on non-AMD systems

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: <stable@...r.kernel.org>
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: Willy Tarreau <w@....eu>
---
 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 59554dc..e6a3b1e 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -67,8 +67,8 @@ 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)
-- 
2.8.0.rc2.1.gbe9624a