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Subject[PATCH 3.12 60/88] x86/amd_nb: Fix boot crash on non-AMD systems
Date
From: Borislav Petkov <bp@suse.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@cybernetics.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.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@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.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
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