| Message ID | 20220901202645.1463552-1-irogers@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | af515a5587b8f45f19e11657746e0c89411b0380 |
| Headers | show |
| Series | [v1] selftests/xsk: Avoid use-after-free on ctx | expand |
On Thu, Sep 1, 2022 at 10:56 PM Ian Rogers <irogers@google.com> wrote: > > The put lowers the reference count to 0 and frees ctx, reading it > afterwards is invalid. Move the put after the uses and determine the > last use by the reference count being 1. Thanks for spotting and fixing this Ian. Acked-by: Magnus Karlsson <magnus.karlsson@intel.com> > Fixes: 39e940d4abfa ("selftests/xsk: Destroy BPF resources only when ctx refcount drops to 0") > Signed-off-by: Ian Rogers <irogers@google.com> > --- > tools/testing/selftests/bpf/xsk.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/tools/testing/selftests/bpf/xsk.c b/tools/testing/selftests/bpf/xsk.c > index f2721a4ae7c5..0b3ff49c740d 100644 > --- a/tools/testing/selftests/bpf/xsk.c > +++ b/tools/testing/selftests/bpf/xsk.c > @@ -1237,15 +1237,15 @@ void xsk_socket__delete(struct xsk_socket *xsk) > ctx = xsk->ctx; > umem = ctx->umem; > > - xsk_put_ctx(ctx, true); > - > - if (!ctx->refcount) { > + if (ctx->refcount == 1) { > xsk_delete_bpf_maps(xsk); > close(ctx->prog_fd); > if (ctx->has_bpf_link) > close(ctx->link_fd); > } > > + xsk_put_ctx(ctx, true); > + > err = xsk_get_mmap_offsets(xsk->fd, &off); > if (!err) { > if (xsk->rx) { > -- > 2.37.2.789.g6183377224-goog >
Hello: This patch was applied to bpf/bpf-next.git (master) by Daniel Borkmann <daniel@iogearbox.net>: On Thu, 1 Sep 2022 13:26:45 -0700 you wrote: > The put lowers the reference count to 0 and frees ctx, reading it > afterwards is invalid. Move the put after the uses and determine the > last use by the reference count being 1. > > Fixes: 39e940d4abfa ("selftests/xsk: Destroy BPF resources only when ctx refcount drops to 0") > Signed-off-by: Ian Rogers <irogers@google.com> > > [...] Here is the summary with links: - [v1] selftests/xsk: Avoid use-after-free on ctx https://git.kernel.org/bpf/bpf-next/c/af515a5587b8 You are awesome, thank you!
diff --git a/tools/testing/selftests/bpf/xsk.c b/tools/testing/selftests/bpf/xsk.c index f2721a4ae7c5..0b3ff49c740d 100644 --- a/tools/testing/selftests/bpf/xsk.c +++ b/tools/testing/selftests/bpf/xsk.c @@ -1237,15 +1237,15 @@ void xsk_socket__delete(struct xsk_socket *xsk) ctx = xsk->ctx; umem = ctx->umem; - xsk_put_ctx(ctx, true); - - if (!ctx->refcount) { + if (ctx->refcount == 1) { xsk_delete_bpf_maps(xsk); close(ctx->prog_fd); if (ctx->has_bpf_link) close(ctx->link_fd); } + xsk_put_ctx(ctx, true); + err = xsk_get_mmap_offsets(xsk->fd, &off); if (!err) { if (xsk->rx) {
The put lowers the reference count to 0 and frees ctx, reading it afterwards is invalid. Move the put after the uses and determine the last use by the reference count being 1. Fixes: 39e940d4abfa ("selftests/xsk: Destroy BPF resources only when ctx refcount drops to 0") Signed-off-by: Ian Rogers <irogers@google.com> --- tools/testing/selftests/bpf/xsk.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)