On 29.06.20 21:21, Joe Perches wrote: > On Mon, 2020-06-29 at 12:54 +0200, David Hildenbrand wrote: >> On 28.06.20 19:37, Joe Perches wrote: >>> On Sun, 2020-06-28 at 17:25 +0200, Bartosz Golaszewski wrote: >>>> From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx> >>>> >>>> Memory allocated with kstrdup_const() must not be passed to regular >>>> krealloc() as it is not aware of the possibility of the chunk residing >>>> in .rodata. Since there are no potential users of krealloc_const() >>>> at the moment, let's just update the doc to make it explicit. >>> >>> Another option would be to return NULL if it's >>> used from krealloc with a pointer into rodata > [] >>> diff --git a/mm/slab_common.c b/mm/slab_common.c > [] >>> @@ -1683,6 +1683,9 @@ static __always_inline void *__do_krealloc(const void *p, size_t new_size, >>> * @new_size: how many bytes of memory are required. >>> * @flags: the type of memory to allocate. >>> * >>> + * If the object pointed to is in rodata (likely from kstrdup_const) >>> + * %NULL is returned. >>> + * > [] >> Won't we have similar issues if somebody would do a kfree() instead of a >> kfree_const()? So I think the original patch makes sense. > > Which is why I also suggested making kfree work for > more types of memory freeing earlier this month. > > https://lore.kernel.org/lkml/573b3fbd5927c643920e1364230c296b23e7584d.camel@xxxxxxxxxxx/ I'm curious, do we see a lot of BUGs that resulted from wrong usage such that we need runtime checks for such things that the code can just statically specify (If I use kstrdup_const() for allocation I can just use kfree_const() for freeing - no runtime checks needed). IOW, what's the real benefit that is worth spending extra runtime cycles? -- Thanks, David / dhildenb
