On 28.06.20 19:37, Joe Perches wrote: > On Sun, 2020-06-28 at 17:25 +0200, Bartosz Golaszewski wrote: >> From: Bartosz Golaszewski <[email protected]> >> >> 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 > --- > mm/slab_common.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 37d48a56431d..f8b49656171b 100644 > --- 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. > + * > * The contents of the object pointed to are preserved up to the > * lesser of the new and old sizes. If @p is %NULL, krealloc() > * behaves exactly like kmalloc(). If @new_size is 0 and @p is not a > @@ -1694,6 +1697,9 @@ void *krealloc(const void *p, size_t new_size, gfp_t > flags) > { > void *ret; > > + if (unlikely(is_kernel_rodata((unsigned long)p))) > + return NULL; > + > if (unlikely(!new_size)) { > kfree(p); > return ZERO_SIZE_PTR; >
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. -- Thanks, David / dhildenb
