[PATCH 3.12 062/175] EDAC, amd64_edac: Prevent OOPS with >16 memory controllers

[Jiri Slaby]

From: Daniel J Blueman <daniel@xxxxxxxxxxxxx>

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

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

commit 0c510cc83bdbaac8406f4f7caef34f4da0ba35ea upstream.

When DRAM errors occur on memory controllers after EDAC_MAX_MCS (16),
the kernel fatally dereferences unallocated structures, see splat below;
this occurs on at least NumaConnect systems.

Fix by checking if a memory controller info structure was found.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000320
IP: [<ffffffff819f714f>] decode_bus_error+0x2f/0x2b0
PGD 2f8b5a3067 PUD 2f8b5a2067 PMD 0
Oops: 0000 [#2] SMP
Modules linked in:
CPU: 224 PID: 11930 Comm: stream_c.exe.gn Tainted: G   D    3.19.0 #1
Hardware name: Supermicro H8QGL/H8QGL, BIOS 3.5b    01/28/2015
task: ffff8807dbfb8c00 ti: ffff8807dd16c000 task.ti: ffff8807dd16c000
RIP: 0010:[<ffffffff819f714f>] [<ffffffff819f714f>] decode_bus_error+0x2f/0x2b0
RSP: 0000:ffff8907dfc03c48 EFLAGS: 00010297
RAX: 0000000000000001 RBX: 9c67400010080a13 RCX: 0000000000001dc6
RDX: 000000001dc61dc6 RSI: ffff8907dfc03df0 RDI: 000000000000001c
RBP: ffff8907dfc03ce8 R08: 0000000000000000 R09: 0000000000000022
R10: ffff891fffa30380 R11: 00000000001cfc90 R12: 0000000000000008
R13: 0000000000000000 R14: 000000000000001c R15: 00009c6740001000
FS: 00007fa97ee18700(0000) GS:ffff8907dfc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000320 CR3: 0000003f889b8000 CR4: 00000000000407e0
Stack:
 0000000000000000 ffff8907dfc03df0 0000000000000008 9c67400010080a13
 000000000000001c 00009c6740001000 ffff8907dfc03c88 ffffffff810e4f9a
 ffff8907dfc03ce8 ffffffff81b375b9 0000000000000000 0000000000000010
Call Trace:
 <IRQ>
 ? vprintk_default
 ? printk
 amd_decode_mce
 notifier_call_chain
 atomic_notifier_call_chain
 mce_log
 machine_check_poll
 mce_timer_fn
 ? mce_cpu_restart
 call_timer_fn.isra.29
 run_timer_softirq
 __do_softirq
 irq_exit
 smp_apic_timer_interrupt
 apic_timer_interrupt
 <EOI>
 ? down_read_trylock
 __do_page_fault
 ? __schedule
 do_page_fault
 page_fault

Signed-off-by: Daniel J Blueman <daniel@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1424144078-24589-1-git-send-email-daniel@xxxxxxxxxxxxx
[ Boris: massage commit message ]
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> [backport to 3.12]
---
 drivers/edac/amd64_edac.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
index d43a6202a5c5..10162af430c5 100644
--- a/drivers/edac/amd64_edac.c
+++ b/drivers/edac/amd64_edac.c
@@ -2043,7 +2043,13 @@ static inline void __amd64_decode_bus_error(struct mem_ctl_info *mci,
 
 void amd64_decode_bus_error(int node_id, struct mce *m)
 {
-	__amd64_decode_bus_error(mcis[node_id], m);
+	struct mem_ctl_info *mci;
+
+	mci = edac_mc_find(node_id);
+	if (!mci)
+		return;
+
+	__amd64_decode_bus_error(mci, m);
 }
 
 /*
-- 
2.3.0

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