| From 3528a4a708f0be7be10eb4172202a3362f617527 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Tue, 25 May 2021 13:20:12 +0100 |
| Subject: random32: Fix implicit truncation warning in prandom_seed_state() |
| |
| From: Richard Fitzgerald <rf@opensource.cirrus.com> |
| |
| [ Upstream commit d327ea15a305024ef0085252fa3657bbb1ce25f5 ] |
| |
| sparse generates the following warning: |
| |
| include/linux/prandom.h:114:45: sparse: sparse: cast truncates bits from |
| constant value |
| |
| This is because the 64-bit seed value is manipulated and then placed in a |
| u32, causing an implicit cast and truncation. A forced cast to u32 doesn't |
| prevent this warning, which is reasonable because a typecast doesn't prove |
| that truncation was expected. |
| |
| Logical-AND the value with 0xffffffff to make explicit that truncation to |
| 32-bit is intended. |
| |
| Reported-by: kernel test robot <lkp@intel.com> |
| Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> |
| Reviewed-by: Petr Mladek <pmladek@suse.com> |
| Signed-off-by: Petr Mladek <pmladek@suse.com> |
| Link: https://lore.kernel.org/r/20210525122012.6336-3-rf@opensource.cirrus.com |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| include/linux/prandom.h | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| diff --git a/include/linux/prandom.h b/include/linux/prandom.h |
| index bbf4b4ad61df..056d31317e49 100644 |
| --- a/include/linux/prandom.h |
| +++ b/include/linux/prandom.h |
| @@ -111,7 +111,7 @@ static inline u32 __seed(u32 x, u32 m) |
| */ |
| static inline void prandom_seed_state(struct rnd_state *state, u64 seed) |
| { |
| - u32 i = (seed >> 32) ^ (seed << 10) ^ seed; |
| + u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL; |
| |
| state->s1 = __seed(i, 2U); |
| state->s2 = __seed(i, 8U); |
| -- |
| 2.30.2 |
| |