linux-kernel - Re: [PATCH bpf-next v4 2/5] bpf: Add dmabuf iterator

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CABdmKX1gxShJu3L11D0-hNMwRArJrzy1UMpuKJY-CSZvAfDh-Q@mail.gmail.com>
Date: Fri, 9 May 2025 10:13:10 -0700
From: "T.J. Mercier" <tjmercier@...gle.com>
To: Song Liu <song@...nel.org>
Cc: sumit.semwal@...aro.org, christian.koenig@....com, ast@...nel.org, 
	daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev, 
	skhan@...uxfoundation.org, alexei.starovoitov@...il.com, 
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org, 
	bpf@...r.kernel.org, linux-kselftest@...r.kernel.org, android-mm@...gle.com, 
	simona@...ll.ch, eddyz87@...il.com, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	jolsa@...nel.org, mykolal@...com, shuah@...nel.org
Subject: Re: [PATCH bpf-next v4 2/5] bpf: Add dmabuf iterator

On Thu, May 8, 2025 at 5:27 PM Song Liu <song@...nel.org> wrote:
>
> On Thu, May 8, 2025 at 11:20 AM T.J. Mercier <tjmercier@...gle.com> wrote:
> >
> > The dmabuf iterator traverses the list of all DMA buffers.
> >
> > DMA buffers are refcounted through their associated struct file. A
> > reference is taken on each buffer as the list is iterated to ensure each
> > buffer persists for the duration of the bpf program execution without
> > holding the list mutex.
> >
> > Signed-off-by: T.J. Mercier <tjmercier@...gle.com>
> > Reviewed-by: Christian König <christian.koenig@....com>
>
> Acked-by: Song Liu <song@...nel.org>
>
> With one nitpick below.

Thanks!

> > ---
> [...]
> > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> > index 8ff4add71f88..7af2ea839f58 100644
> > --- a/include/linux/dma-buf.h
> > +++ b/include/linux/dma-buf.h
> > @@ -634,4 +634,6 @@ int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map);
> >  void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map);
> >  int dma_buf_vmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map);
> >  void dma_buf_vunmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map);
> > +struct dma_buf *dma_buf_iter_begin(void);
> > +struct dma_buf *dma_buf_iter_next(struct dma_buf *dmbuf);
> >  #endif /* __DMA_BUF_H__ */
> > diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
> > index 70502f038b92..3a335c50e6e3 100644
> > --- a/kernel/bpf/Makefile
> > +++ b/kernel/bpf/Makefile
> > @@ -53,6 +53,9 @@ obj-$(CONFIG_BPF_SYSCALL) += relo_core.o
> >  obj-$(CONFIG_BPF_SYSCALL) += btf_iter.o
> >  obj-$(CONFIG_BPF_SYSCALL) += btf_relocate.o
> >  obj-$(CONFIG_BPF_SYSCALL) += kmem_cache_iter.o
> > +ifeq ($(CONFIG_DMA_SHARED_BUFFER),y)
> > +obj-$(CONFIG_BPF_SYSCALL) += dmabuf_iter.o
> > +endif
> >
> >  CFLAGS_REMOVE_percpu_freelist.o = $(CC_FLAGS_FTRACE)
> >  CFLAGS_REMOVE_bpf_lru_list.o = $(CC_FLAGS_FTRACE)
> > diff --git a/kernel/bpf/dmabuf_iter.c b/kernel/bpf/dmabuf_iter.c
> > new file mode 100644
> > index 000000000000..96b4ba7f0b2c
> > --- /dev/null
> > +++ b/kernel/bpf/dmabuf_iter.c
> > @@ -0,0 +1,102 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/* Copyright (c) 2025 Google LLC */
> > +#include <linux/bpf.h>
> > +#include <linux/btf_ids.h>
> > +#include <linux/dma-buf.h>
> > +#include <linux/kernel.h>
> > +#include <linux/seq_file.h>
> > +
> > +BTF_ID_LIST_SINGLE(bpf_dmabuf_btf_id, struct, dma_buf)
> > +DEFINE_BPF_ITER_FUNC(dmabuf, struct bpf_iter_meta *meta, struct dma_buf *dmabuf)
>
> nit: It is better to move these two lines later, to where they
> are about to be used.

I've moved them both to just before dmabuf_iter_init() farther down.