linux-kernel - [PATCH 01/11] random: don't feed stack data into pool when interrupt regs NULL

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Message-Id: <1380572952-30729-2-git-send-email-andi@firstfloor.org>
Date:	Mon, 30 Sep 2013 13:29:02 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	linux-kernel@...r.kernel.org
Cc:	Andi Kleen <ak@...ux.intel.com>, tony.luck@...el.com, tytso@....edu
Subject: [PATCH 01/11] random: don't feed stack data into pool when interrupt regs NULL

From: Andi Kleen <ak@...ux.intel.com>

In some cases, e.g. after this

arch/ia64/kernel/irq.c:185:                     struct pt_regs *old_regs = set_irq_regs(NULL);
arch/ia64/kernel/irq_ia64.c:560:                        struct pt_regs *old_regs = set_irq_regs(NULL);

the regs passed to add_interrupt_randomness() could be NULL.

In this case fast_mix would use two uninitialized ints from the stack
and mix it into the pool.

In this case set the input to 0.

Cc: tony.luck@...el.com
Cc: tytso@....edu
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 drivers/char/random.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 7737b5b..25ed2dc 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -752,6 +752,8 @@ void add_interrupt_randomness(int irq, int irq_flags)
 		__u64 ip = instruction_pointer(regs);
 		input[2] = ip;
 		input[3] = ip >> 32;
+	} else {
+		input[2] = input[3] = 0;
 	}
 
 	fast_mix(fast_pool, input, sizeof(input));
-- 
1.8.3.1

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