From: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx> Subject: lib/stackdepot.c: replace one-element array with flexible-array member Patch series "] lib/stackdepot.c: Replace one-element array with flexible-array member". This series aims to replace a one-element array with a flexible-array member. Also, make use of the struct_size(), flexible_array_size() and array_size() helpers. This patch (of 3): There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. Refactor the code according to the use of a flexible-array member in struct stack_record, instead of a one-element array, and use the struct_size() helper to calculate the size for the allocation. [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays Link: https://lkml.kernel.org/r/cover.1601565471.git.gustavoars@xxxxxxxxxx Link: https://lore.kernel.org/lkml/5f75876b.x9zdN10esiC0qLHV%25lkp@xxxxxxxxx/ Link: https://lkml.kernel.org/r/2f1e6a17aaa891ad9c58817cf0a10b8ab8894f59.1601565471.git.gustavoars@xxxxxxxxxx Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/stackdepot.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- a/lib/stackdepot.c~lib-stackdepotc-replace-one-element-array-with-flexible-array-member +++ a/lib/stackdepot.c @@ -62,7 +62,7 @@ struct stack_record { u32 hash; /* Hash in the hastable */ u32 size; /* Number of frames in the stack */ union handle_parts handle; - unsigned long entries[1]; /* Variable-sized array of entries. */ + unsigned long entries[]; /* Variable-sized array of entries. */ }; static void *stack_slabs[STACK_ALLOC_MAX_SLABS]; @@ -104,9 +104,8 @@ static bool init_stack_slab(void **preal static struct stack_record *depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc, gfp_t alloc_flags) { - int required_size = offsetof(struct stack_record, entries) + - sizeof(unsigned long) * size; struct stack_record *stack; + size_t required_size = struct_size(stack, entries, size); required_size = ALIGN(required_size, 1 << STACK_ALLOC_ALIGN); _
