RE: [PATCH v17 1/2] eal: remove alloc_size from rte_lcore_var_alloc

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Scott Mitchell <scott.k.mitch1@gmail.com>
> 
> The __rte_alloc_size(1) attribute on rte_lcore_var_alloc() is
> semantically incorrect and causes false positives with FORTIFY_SOURCE
> runtime checks.
> 
> The attribute tells the compiler that the function returns a pointer
> to 'size' bytes of usable memory. However, rte_lcore_var_alloc()
> actually returns a handle to a per-lcore variable scheme. The
> allocator internally allocates 'size' bytes per lcore
> (size * RTE_MAX_LCORE total), partitioned into per-lcore sections.
> The handle points to lcore 0's copy, and accessed via
> RTE_LCORE_VAR_LCORE(lcore_id, handle) which computes:
> handle + (lcore_id * RTE_MAX_LCORE_VAR). Access is expected
> beyond 'size' bytes beyond the returned pointer when 'lcore_id != 0'
> but FORTIFY_SOURCE may terminate the program due to out of bounds
> access.
> 
> This can be observed on CI with gcc 13.3.0 in lcore_var_autotest with
> '*** buffer overflow detected ***: terminated' if pointer provenance
> is preserved (e.g. if offsets avoid casting to uintptr_t).
> 
> Fixes: 5bce9bed67ad ("eal: add static per-lcore memory allocation
> facility")
> Cc: mattias.ronnblom@ericsson.com
> Cc: stable@dpdk.org
> 
> Signed-off-by: Scott Mitchell <scott.k.mitch1@gmail.com>
> ---
>  lib/eal/include/rte_lcore_var.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/eal/include/rte_lcore_var.h
> b/lib/eal/include/rte_lcore_var.h
> index ca31dff6fd..48b022e84e 100644
> --- a/lib/eal/include/rte_lcore_var.h
> +++ b/lib/eal/include/rte_lcore_var.h
> @@ -202,7 +202,7 @@ rte_lcore_var_lcore(unsigned int lcore_id, void
> *handle)
>  __rte_experimental
>  void *
>  rte_lcore_var_alloc(size_t size, size_t align)
> -	__rte_alloc_size(1) __rte_alloc_align(2);
> +	__rte_alloc_align(2);
> 
>  #ifdef __cplusplus
>  }
> --
> 2.39.5 (Apple Git-154)

This patch could be separated from the RTE_PTR_ADD/SUB series.

Acked-by: Morten Brørup <mb@smartsharesystems.com>

NB: Please keep this ACK for any new versions of this patch if the essence of the patch doesn't change.