From: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx> [ 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@xxxxxxxxx> Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx> Reviewed-by: Petr Mladek <pmladek@xxxxxxxx> Signed-off-by: Petr Mladek <pmladek@xxxxxxxx> Link: https://lore.kernel.org/r/20210525122012.6336-3-rf@xxxxxxxxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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
