On Mon, Oct 31, 2022 at 02:53:35PM -0700, Stanislav Fomichev wrote:
> On Fri, Oct 28, 2022 at 7:54 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> >
> > Since the full kmalloc bucket size is being explicitly allocated, pass
> > back the resulting details to take advantage of the full size so that
> > reallocation checking will be needed less frequently.
> >
> > Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
> > Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> > Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> > Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
> > Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx>
> > Cc: Song Liu <song@xxxxxxxxxx>
> > Cc: Yonghong Song <yhs@xxxxxx>
> > Cc: KP Singh <kpsingh@xxxxxxxxxx>
> > Cc: Stanislav Fomichev <sdf@xxxxxxxxxx>
> > Cc: Hao Luo <haoluo@xxxxxxxxxx>
> > Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> > Cc: bpf@xxxxxxxxxxxxxxx
> > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > ---
> > kernel/bpf/verifier.c | 27 ++++++++++++++++-----------
> > 1 file changed, 16 insertions(+), 11 deletions(-)
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 1c040d27b8f6..e58b554e862b 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -1020,20 +1020,23 @@ static void *copy_array(void *dst, const void *src, size_t n, size_t size, gfp_t
> > return dst ? dst : ZERO_SIZE_PTR;
> > }
> >
> > -/* resize an array from old_n items to new_n items. the array is reallocated if it's too
> > - * small to hold new_n items. new items are zeroed out if the array grows.
> > +/* Resize an array from old_n items to *new_n items. The array is
> > + * reallocated if it's too small to hold *new_n items. New items are
> > + * zeroed out if the array grows. Allocation is rounded up to next kmalloc
> > + * bucket size to reduce frequency of resizing. *new_n contains the new
> > + * total number of items that will fit.
> > *
> > - * Contrary to krealloc_array, does not free arr if new_n is zero.
> > + * Contrary to krealloc, does not free arr if new_n is zero.
> > */
> > -static void *realloc_array(void *arr, size_t old_n, size_t new_n, size_t size)
> > +static void *realloc_array(void *arr, size_t old_n, size_t *new_n, size_t size)
> > {
> > size_t alloc_size;
> > void *new_arr;
> >
> > - if (!new_n || old_n == new_n)
> > + if (!new_n || !*new_n || old_n == *new_n)
> > goto out;
> >
> > - alloc_size = kmalloc_size_roundup(size_mul(new_n, size));
> > + alloc_size = kmalloc_size_roundup(size_mul(*new_n, size));
> > new_arr = krealloc(arr, alloc_size, GFP_KERNEL);
> > if (!new_arr) {
> > kfree(arr);
> > @@ -1041,8 +1044,9 @@ static void *realloc_array(void *arr, size_t old_n, size_t new_n, size_t size)
> > }
> > arr = new_arr;
> >
> > - if (new_n > old_n)
> > - memset(arr + old_n * size, 0, (new_n - old_n) * size);
> > + *new_n = alloc_size / size;
> > + if (*new_n > old_n)
> > + memset(arr + old_n * size, 0, (*new_n - old_n) * size);
> >
> > out:
> > return arr ? arr : ZERO_SIZE_PTR;
>
> [..]
>
> > @@ -1074,7 +1078,7 @@ static int copy_stack_state(struct bpf_func_state *dst, const struct bpf_func_st
> >
> > static int resize_reference_state(struct bpf_func_state *state, size_t n)
> > {
> > - state->refs = realloc_array(state->refs, state->acquired_refs, n,
> > + state->refs = realloc_array(state->refs, state->acquired_refs, &n,
> > sizeof(struct bpf_reference_state));
> > if (!state->refs)
> > return -ENOMEM;
>
> Patches 1 & 2 look good, but not sure about this part. We later do the
> following in the same routine:
I'm totally fine leaving off #3. 1 is a bug fix, 2 is what I need to get
the ksize side-effect managed in bpf, and 3 was maybe an optimization.
--
Kees Cook
