Re: [dpdk-dev] [PATCH] librte_acl: fix undefined behavior

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Aaron,

> 
> Left-shift of an integer constant is represented as 'int' type, but a left
> shift of 1 by 31 bits in 'int' is undefined.  Use the U suffix to force
> a representation as unsigned.
> 
> Caught while running with ubsan under gcc.
> 
> Fixes: dc276b5780c2 ("acl: new library")
> Cc: Konstantin Ananyev <konstantin.ananyev@intel.com>
> Signed-off-by: Aaron Conole <aconole@redhat.com>
> ---
> I could have changed the sizeof(bits_t) * 8 in the bitset.bits as well during
> the cleanup, but chose not to to keep the change minimal.

But it seems that you did change it in some places:
 
> -				1 << (n % (sizeof(bits_t) * 8));
> +				1U << (n % (sizeof(bits_t) * CHAR_BIT));

While in others kept unchanged:
> -				(1 << (n % (sizeof(bits_t) * 8)))) {
> +				(1U << (n % (sizeof(bits_t) * 8)))) {

Was that intended?
Konstantin

> 
>  lib/librte_acl/acl_bld.c | 6 +++---
>  lib/librte_acl/acl_gen.c | 4 ++--
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/librte_acl/acl_bld.c b/lib/librte_acl/acl_bld.c
> index b82191f42..9d27c0a5a 100644
> --- a/lib/librte_acl/acl_bld.c
> +++ b/lib/librte_acl/acl_bld.c
> @@ -320,7 +320,7 @@ acl_add_ptr_range(struct acl_build_context *context,
>  	for (n = 0; n < UINT8_MAX + 1; n++)
>  		if (n >= low && n <= high)
>  			bitset.bits[n / (sizeof(bits_t) * 8)] |=
> -				1 << (n % (sizeof(bits_t) * 8));
> +				1U << (n % (sizeof(bits_t) * CHAR_BIT));
> 
>  	return acl_add_ptr(context, root, node, &bitset);
>  }
> @@ -343,7 +343,7 @@ acl_gen_mask(struct rte_acl_bitset *bitset, uint32_t value, uint32_t mask)
>  		if ((n & mask) == value) {
>  			range++;
>  			bitset->bits[n / (sizeof(bits_t) * 8)] |=
> -				1 << (n % (sizeof(bits_t) * 8));
> +				1U << (n % (sizeof(bits_t) * CHAR_BIT));
>  		}
>  	}
>  	return range;
> @@ -972,7 +972,7 @@ build_trie(struct acl_build_context *context, struct rte_acl_build_rule *head,
>  				sizeof(*end->mrt));
> 
>  		for (m = context->cfg.num_categories; 0 != m--; ) {
> -			if (rule->f->data.category_mask & (1 << m)) {
> +			if (rule->f->data.category_mask & (1U << m)) {
>  				end->mrt->results[m] = rule->f->data.userdata;
>  				end->mrt->priority[m] = rule->f->data.priority;
>  			} else {
> diff --git a/lib/librte_acl/acl_gen.c b/lib/librte_acl/acl_gen.c
> index 35a0140b4..81dec3aa6 100644
> --- a/lib/librte_acl/acl_gen.c
> +++ b/lib/librte_acl/acl_gen.c
> @@ -133,7 +133,7 @@ acl_node_fill_dfa(const struct rte_acl_node *node,
>  		for (n = 0; n < RTE_ACL_DFA_SIZE; n++) {
> 
>  			if (bits->bits[n / (sizeof(bits_t) * CHAR_BIT)] &
> -				(1 << (n % (sizeof(bits_t) * CHAR_BIT)))) {
> +				(1U << (n % (sizeof(bits_t) * CHAR_BIT)))) {
> 
>  				dfa[n] = resolved ? child->node_index : x;
>  				ranges += (last_bit == 0);
> @@ -175,7 +175,7 @@ acl_count_sequential_groups(struct rte_acl_bitset *bits, int zero_one)
>  	}
>  	for (n = 0; n < QRANGE_MIN; n++) {
>  		if (bits->bits[n / (sizeof(bits_t) * 8)] &
> -				(1 << (n % (sizeof(bits_t) * 8)))) {
> +				(1U << (n % (sizeof(bits_t) * 8)))) {
>  			if (zero_one == 1 && last_bit != 1)
>  				ranges++;
>  			last_bit = 1;
> --



> 2.21.0