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From: Quentin Casasnovas <quentin.casasnovas@oracle.com>
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Date: Tue, 3 Feb 2015 13:00:22 +0100
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Subject: [PATCH] x86/microcode/intel: Guard against stack overflow in the
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 loader
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mc_saved_tmp is a static array allocated on the stack, we need to make
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sure mc_saved_count stays within its bounds, otherwise we're overflowing
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the stack in _save_mc(). A specially crafted microcode header could lead
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to a kernel crash or potentially kernel execution.
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Signed-off-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>
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Cc: "H. Peter Anvin" <hpa@zytor.com>
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Cc: Fenghua Yu <fenghua.yu@intel.com>
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Link: http://lkml.kernel.org/r/1422964824-22056-1-git-send-email-quentin.casasnovas@oracle.com
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Signed-off-by: Borislav Petkov <bp@suse.de>
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---
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 arch/x86/kernel/cpu/microcode/intel_early.c | 2 +-
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 1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/arch/x86/kernel/cpu/microcode/intel_early.c b/arch/x86/kernel/cpu/microcode/intel_early.c
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index ec9df6f9cd47..5e109a31f62b 100644
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--- a/arch/x86/kernel/cpu/microcode/intel_early.c
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+++ b/arch/x86/kernel/cpu/microcode/intel_early.c
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@@ -321,7 +321,7 @@ get_matching_model_microcode(int cpu, unsigned long start,
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 	unsigned int mc_saved_count = mc_saved_data->mc_saved_count;
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 	int i;
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-	while (leftover) {
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+	while (leftover && mc_saved_count < ARRAY_SIZE(mc_saved_tmp)) {
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 		mc_header = (struct microcode_header_intel *)ucode_ptr;
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 		mc_size = get_totalsize(mc_header);
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-- 
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2.1.0
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