RE: [PATCH v2] hash: fix pointer alignment

[Marat Khalili <marat.khalili@huawei.com>]

> -----Original Message-----
> From: Radu Nicolau <radu.nicolau@intel.com>
> Sent: Friday 27 February 2026 09:48
> To: dev@dpdk.org
> Cc: Marat Khalili <marat.khalili@huawei.com>; Radu Nicolau <radu.nicolau@intel.com>; stable@dpdk.org;
> stephen@networkplumber.org; Yipeng Wang <yipeng1.wang@intel.com>; Sameh Gobriel
> <sameh.gobriel@intel.com>; Bruce Richardson <bruce.richardson@intel.com>; Vladimir Medvedkin
> <vladimir.medvedkin@intel.com>; Pablo de Lara <pablo.de.lara.guarch@intel.com>; Yerden Zhumabekov
> <e_zhumabekov@sts.kz>
> Subject: [PATCH v2] hash: fix pointer alignment
> 
> rte_hash_crc assumes input pointer address is 8 byte aligned
> which may not be always the case.
> This fix aligns the input pointer before proceeding to process it
> in 8 byte chunks.
> 
> Fixes: 504a29af13a7 ("hash: fix strict-aliasing for CRC")
> Cc: stable@dpdk.org
> Cc: stephen@networkplumber.org
> 
> Signed-off-by: Radu Nicolau <radu.nicolau@intel.com>
> ---
> v2: reverse the order of alignment adjustment calls
> 
>  lib/hash/rte_hash_crc.h | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/lib/hash/rte_hash_crc.h b/lib/hash/rte_hash_crc.h
> index fa07c97685..d61420868a 100644
> --- a/lib/hash/rte_hash_crc.h
> +++ b/lib/hash/rte_hash_crc.h
> @@ -127,6 +127,24 @@ rte_hash_crc(const void *data, uint32_t data_len, uint32_t init_val)
>  	unsigned i;
>  	uintptr_t pd = (uintptr_t) data;
> 
> +	/* align input to 8 byte boundary if needed */
> +	if ((pd & 0x7) && data_len >= 8) {
> +		uintptr_t unaligned_bytes = 8 - (pd & 0x7);
> +		data_len -= unaligned_bytes;
> +		if (unaligned_bytes & 0x1) {
> +			init_val = rte_hash_crc_1byte(*(const uint8_t *)pd, init_val);
> +			pd += 1;
> +		}
> +		if (unaligned_bytes & 0x2) {
> +			init_val = rte_hash_crc_2byte(*(const uint16_t *)pd, init_val);
> +			pd += 2;
> +		}
> +		if (unaligned_bytes & 0x4) {
> +			init_val = rte_hash_crc_4byte(*(const uint32_t *)pd, init_val);
> +			pd += 4;
> +		}
> +	}
> +
>  	for (i = 0; i < data_len / 8; i++) {
>  		init_val = rte_hash_crc_8byte(*(const uint64_t *)pd, init_val);
>  		pd += 8;
> --
> 2.52.0
> 

Surprisingly, we do not seem to have any tests calling rte_hash_crc with misaligned data. I tried to tweak existing ones in test_hash.c and test_hash_functions.c, and found out that rte_hash_crc still fails (with ubsan) for sizes less than 8 in one of the last 3 if's, and also that jhash has the same problems. Still this commit is a step in the right direction IMO, so:

Acked-by: Marat Khalili <marat.khalili@huawei.com>