From 203abd67b75f7714ce98ab0cdbd6cfd7ad79dec4 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Mon, 15 Jun 2009 14:52:01 +0200 Subject: x86: mce: Handle banks == 0 case in K7 quirk Vegard Nossum reported: > I get an MCE-related crash like this in latest linus tree: > > [ 0.115341] CPU: L1 I Cache: 64K (64 bytes/line), D cache 64K (64 bytes/line) > [ 0.116396] CPU: L2 Cache: 512K (64 bytes/line) > [ 0.120570] mce: CPU supports 0 MCE banks > [ 0.124870] BUG: unable to handle kernel NULL pointer dereference at 00000000 00000010 > [ 0.128001] IP: [] mcheck_init+0x278/0x320 > [ 0.128001] PGD 0 > [ 0.128001] Thread overran stack, or stack corrupted > [ 0.128001] Oops: 0002 [#1] PREEMPT SMP > [ 0.128001] last sysfs file: > [ 0.128001] CPU 0 > [ 0.128001] Modules linked in: > [ 0.128001] Pid: 0, comm: swapper Not tainted 2.6.30 #426 > [ 0.128001] RIP: 0010:[] [] mcheck_init+0x278/0x320 > [ 0.128001] RSP: 0018:ffffffff81595e38 EFLAGS: 00000246 > [ 0.128001] RAX: 0000000000000010 RBX: ffffffff8158f900 RCX: 0000000000000000 > [ 0.128001] RDX: 0000000000000000 RSI: 00000000000000ff RDI: 0000000000000010 > [ 0.128001] RBP: ffffffff81595e68 R08: 0000000000000001 R09: 0000000000000000 > [ 0.128001] R10: 0000000000000010 R11: 0000000000000000 R12: 0000000000000000 > [ 0.128001] R13: 00000000ffffffff R14: 0000000000000000 R15: 0000000000000000 > [ 0.128001] FS: 0000000000000000(0000) GS:ffff880002288000(0000) knlGS:00000 > 00000000000 > [ 0.128001] CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b > [ 0.128001] CR2: 0000000000000010 CR3: 0000000001001000 CR4: 00000000000006b0 > [ 0.128001] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 0.128001] DR3: 0000000000000000 DR6: 0000000000000000 DR7: 0000000000000000 > [ 0.128001] Process swapper (pid: 0, threadinfo ffffffff81594000, task ffffff > ff8152a4a0) > [ 0.128001] Stack: > [ 0.128001] 0000000081595e68 5aa50ed3b4ddbe6e ffffffff8158f900 ffffffff8158f > 914 > [ 0.128001] ffffffff8158f948 0000000000000000 ffffffff81595eb8 ffffffff813b8 > 69c > [ 0.128001] 5aa50ed3b4ddbe6e 00000001078bfbfd 0000062300000800 5aa50ed3b4ddb > e6e > [ 0.128001] Call Trace: > [ 0.128001] [] identify_cpu+0x331/0x392 > [ 0.128001] [] identify_boot_cpu+0x23/0x6e > [ 0.128001] [] check_bugs+0x1c/0x60 > [ 0.128001] [] start_kernel+0x403/0x46e > [ 0.128001] [] x86_64_start_reservations+0xac/0xd5 > [ 0.128001] [] x86_64_start_kernel+0x115/0x14b > [ 0.128001] [] ? early_idt_handler+0x0/0x71 This happens on QEMU which reports MCA capability, but no banks. Without this patch there is a buffer overrun and boot ops because the code would try to initialize the 0 element of a zero length kmalloc() buffer. Reported-by: Vegard Nossum Tested-by: Pekka Enberg Signed-off-by: Andi Kleen LKML-Reference: <20090615125200.GD31969@one.firstfloor.org> Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/mcheck/mce.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index fabba15e455..d9d77cfd8cc 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -1245,7 +1245,7 @@ static void mce_cpu_quirks(struct cpuinfo_x86 *c) * Various K7s with broken bank 0 around. Always disable * by default. */ - if (c->x86 == 6) + if (c->x86 == 6 && banks > 0) bank[0] = 0; } -- cgit v1.2.3