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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Theodore Ts'o <tytso@mit.edu>,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 5.17 20/43] random: round-robin registers as ulong, not u32
Date:   Mon, 28 Mar 2022 07:18:04 -0400
Message-Id: <20220328111828.1554086-20-sashal@kernel.org>
In-Reply-To: <20220328111828.1554086-1-sashal@kernel.org>
References: <20220328111828.1554086-1-sashal@kernel.org>
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From: "Jason A. Donenfeld" <Jason@zx2c4.com>

[ Upstream commit da3951ebdcd1cb1d5c750e08cd05aee7b0c04d9a ]

When the interrupt handler does not have a valid cycle counter, it calls
get_reg() to read a register from the irq stack, in round-robin.
Currently it does this assuming that registers are 32-bit. This is
_probably_ the case, and probably all platforms without cycle counters
are in fact 32-bit platforms. But maybe not, and either way, it's not
quite correct. This commit fixes that to deal with `unsigned long`
rather than `u32`.

Cc: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/char/random.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 2f21c5473d86..d2ce6b1a229d 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1032,15 +1032,15 @@ static void add_interrupt_bench(cycles_t start)
 #define add_interrupt_bench(x)
 #endif
 
-static u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
+static unsigned long get_reg(struct fast_pool *f, struct pt_regs *regs)
 {
-	u32 *ptr = (u32 *)regs;
+	unsigned long *ptr = (unsigned long *)regs;
 	unsigned int idx;
 
 	if (regs == NULL)
 		return 0;
 	idx = READ_ONCE(f->reg_idx);
-	if (idx >= sizeof(struct pt_regs) / sizeof(u32))
+	if (idx >= sizeof(struct pt_regs) / sizeof(unsigned long))
 		idx = 0;
 	ptr += idx++;
 	WRITE_ONCE(f->reg_idx, idx);
-- 
2.34.1