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Subject[PATCH 5.18 12/47] riscv: use fallback for random_get_entropy() instead of zero
Date
From: "Jason A. Donenfeld" <Jason@zx2c4.com>

commit 6d01238623faa9425f820353d2066baf6c9dc872 upstream.

In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/riscv/include/asm/timex.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/riscv/include/asm/timex.h
+++ b/arch/riscv/include/asm/timex.h
@@ -41,7 +41,7 @@ static inline u32 get_cycles_hi(void)
static inline unsigned long random_get_entropy(void)
{
if (unlikely(clint_time_val == NULL))
- return 0;
+ return random_get_entropy_fallback();
return get_cycles();
}
#define random_get_entropy() random_get_entropy()

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