On Tue, Nov 15, 2022 at 05:31:29AM +0530, Kumar Kartikeya Dwivedi wrote: > It may happen that destination buffer memory overlaps with memory dynptr > points to. Hence, we must use memmove to correctly copy from dynptr to > destination buffer, or source buffer to dynptr. > > This actually isn't a problem right now, as memcpy implementation falls > back to memmove on detecting overlap and warns about it, but we > shouldn't be relying on that. > > Acked-by: Joanne Koong <joannelkoong@xxxxxxxxx> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> > --- Good call, thanks for this. Acked-by: David Vernet <void@xxxxxxxxxxxxx> > kernel/bpf/helpers.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 714f5c9d0c1f..1099ed1e7712 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -1489,7 +1489,7 @@ BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len, const struct bpf_dynptr_kern > if (err) > return err; > > - memcpy(dst, src->data + src->offset + offset, len); > + memmove(dst, src->data + src->offset + offset, len); Can you add a comment here and in bpf_dynptr_write() which explain why memmove is needed? > > return 0; > } > @@ -1517,7 +1517,7 @@ BPF_CALL_5(bpf_dynptr_write, const struct bpf_dynptr_kern *, dst, u32, offset, v > if (err) > return err; > > - memcpy(dst->data + dst->offset + offset, src, len); > + memmove(dst->data + dst->offset + offset, src, len); > > return 0; > } > -- > 2.38.1 >
