RE: [PATCH v3 09/18] stack: fix unaligned accesses on 128-bit

[Konstantin Ananyev <konstantin.ananyev@huawei.com>]

> -----Original Message-----
> From: David Marchand <david.marchand@redhat.com>
> Sent: Tuesday, July 8, 2025 1:28 PM
> To: dev@dpdk.org
> Cc: stable@dpdk.org; Bruce Richardson <bruce.richardson@intel.com>; Gage Eads <gage.eads@intel.com>; Olivier Matz
> <olivier.matz@6wind.com>; Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Subject: [PATCH v3 09/18] stack: fix unaligned accesses on 128-bit
> 
> Caught by UBSan:
> 
> ../lib/eal/x86/include/rte_atomic_64.h:206:21: runtime error:
> 	member access within misaligned address 0x7ffd9c67f228 for
> 	type 'const rte_int128_t', which requires 16 byte alignment
> 	0x7ffd9c67f228: note: pointer points here
>  00 00 00 00  c0 5d 3e 00 01 00 00 00  01 00 00 00 00 00 00 00
>               ^
>  00 00 00 00 00 00 00 00  00 00 00 00
> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
> 	../lib/eal/x86/include/rte_atomic_64.h:206:21 in
> 	../lib/eal/x86/include/rte_atomic_64.h:206:21: runtime error:
> 	member access within misaligned address 0x7ffd9c67f228 for type
> 	'const union rte_int128_t::(anonymous at
> 	../lib/eal/include/generic/rte_atomic.h:1102:2)', which requires
> 	16 byte alignment
> 0x7ffd9c67f228: note: pointer points here
>  00 00 00 00  c0 5d 3e 00 01 00 00 00  01 00 00 00 00 00 00 00
>               ^
>  00 00 00 00 00 00 00 00  00 00 00 00
> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
> 	../lib/eal/x86/include/rte_atomic_64.h:206:21 in
> 	../lib/eal/x86/include/rte_atomic_64.h:206:16: runtime error:
> 	load of misaligned address 0x7ffd9c67f228 for type
> 	'const uint64_t' (aka 'const unsigned long'), which requires
> 	16 byte alignment
> 0x7ffd9c67f228: note: pointer points here
>  00 00 00 00  c0 5d 3e 00 01 00 00 00  01 00 00 00 00 00 00 00
>               ^
>  00 00 00 00 00 00 00 00  00 00 00 00
> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
> 	../lib/eal/x86/include/rte_atomic_64.h:206:21 in
> 
> Fixes: 3340202f5954 ("stack: add lock-free implementation")
> Cc: stable@dpdk.org
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> Acked-by: Bruce Richardson <bruce.richardson@intel.com>
> ---
>  lib/stack/rte_stack_lf_c11.h     | 8 ++++----
>  lib/stack/rte_stack_lf_generic.h | 8 ++++----
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/stack/rte_stack_lf_c11.h b/lib/stack/rte_stack_lf_c11.h
> index b97e02d6a1..f674731235 100644
> --- a/lib/stack/rte_stack_lf_c11.h
> +++ b/lib/stack/rte_stack_lf_c11.h
> @@ -63,13 +63,13 @@ __rte_stack_lf_push_elems(struct rte_stack_lf_list *list,
>  			  struct rte_stack_lf_elem *last,
>  			  unsigned int num)
>  {
> -	struct rte_stack_lf_head old_head;
> +	alignas(16) struct rte_stack_lf_head old_head;
>  	int success;
> 
>  	old_head = list->head;
> 
>  	do {
> -		struct rte_stack_lf_head new_head;
> +		alignas(16) struct rte_stack_lf_head new_head;
> 
>  		/* Swing the top pointer to the first element in the list and
>  		 * make the last element point to the old top.
> @@ -102,7 +102,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,
>  			 void **obj_table,
>  			 struct rte_stack_lf_elem **last)
>  {
> -	struct rte_stack_lf_head old_head;
> +	alignas(16) struct rte_stack_lf_head old_head;
>  	uint64_t len;
>  	int success = 0;
> 
> @@ -129,7 +129,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,
> 
>  	/* Pop num elements */
>  	do {
> -		struct rte_stack_lf_head new_head;
> +		alignas(16) struct rte_stack_lf_head new_head;
>  		struct rte_stack_lf_elem *tmp;
>  		unsigned int i;
> 
> diff --git a/lib/stack/rte_stack_lf_generic.h b/lib/stack/rte_stack_lf_generic.h
> index cc69e4d168..32f56dffdd 100644
> --- a/lib/stack/rte_stack_lf_generic.h
> +++ b/lib/stack/rte_stack_lf_generic.h
> @@ -36,13 +36,13 @@ __rte_stack_lf_push_elems(struct rte_stack_lf_list *list,
>  			  struct rte_stack_lf_elem *last,
>  			  unsigned int num)
>  {
> -	struct rte_stack_lf_head old_head;
> +	alignas(16) struct rte_stack_lf_head old_head;
>  	int success;
> 
>  	old_head = list->head;
> 
>  	do {
> -		struct rte_stack_lf_head new_head;
> +		alignas(16) struct rte_stack_lf_head new_head;
> 
>  		/* An acquire fence (or stronger) is needed for weak memory
>  		 * models to establish a synchronized-with relationship between
> @@ -77,7 +77,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,
>  			 void **obj_table,
>  			 struct rte_stack_lf_elem **last)
>  {
> -	struct rte_stack_lf_head old_head;
> +	alignas(16) struct rte_stack_lf_head old_head;
>  	int success = 0;
> 
>  	/* Reserve num elements, if available */
> @@ -99,7 +99,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,
> 
>  	/* Pop num elements */
>  	do {
> -		struct rte_stack_lf_head new_head;
> +		alignas(16) struct rte_stack_lf_head new_head;
>  		struct rte_stack_lf_elem *tmp;
>  		unsigned int i;
> 
> --

Acked-by: Konstantin Ananyev <konstantin.ananyev@huawei.com>
 


> 2.50.0