Messages in this thread Patch in this message | | | From | Richard Fitzgerald <> | Subject | [PATCH v2 2/2] random32: Fix implicit truncation warning in prandom_seed_state() | Date | Tue, 25 May 2021 13:20:12 +0100 |
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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> --- 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); -- 2.20.1
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