tree 631ca42e766b96409ffb640442c0e935f7c1894d
parent 0dc42e73fa05c12277544b99c5d5d9b4c04118e4
author He Gao <hegao@google.com> 1755558455 +0000
committer Robert Kolchmeyer <rkolchmeyer@google.com> 1755812682 -0700

bpf: Fix oob access in cgroup local storage

upstream commit: abad3d0bad72a52137e0c350c59542d75ae4f513

Lonial reported that an out-of-bounds access in cgroup local storage
can be crafted via tail calls. Given two programs each utilizing a
cgroup local storage with a different value size, and one program
doing a tail call into the other. The verifier will validate each of
the indivial programs just fine. However, in the runtime context
the bpf_cg_run_ctx holds an bpf_prog_array_item which contains the
BPF program as well as any cgroup local storage flavor the program
uses. Helpers such as bpf_get_local_storage() pick this up from the
runtime context:

  ctx = container_of(current->bpf_ctx, struct bpf_cg_run_ctx, run_ctx);
  storage = ctx->prog_item->cgroup_storage[stype];

  if (stype == BPF_CGROUP_STORAGE_SHARED)
    ptr = &READ_ONCE(storage->buf)->data[0];
  else
    ptr = this_cpu_ptr(storage->percpu_buf);

For the second program which was called from the originally attached
one, this means bpf_get_local_storage() will pick up the former
program's map, not its own. With mismatching sizes, this can result
in an unintended out-of-bounds access.

To fix this issue, we need to extend bpf_map_owner with an array of
storage_cookie[] to match on i) the exact maps from the original
program if the second program was using bpf_get_local_storage(), or
ii) allow the tail call combination if the second program was not
using any of the cgroup local storage maps.

BUG=b/438183338
TEST=presubmit
RELEASE_NOTE=Fixed KCTF-abad3d0 in the Linux kernel.

cos-patch: security-high
Fixes: 7d9c3427894f ("bpf: Make cgroup storages shared between programs on the same cgroup")
Reported-by: Lonial Con <kongln9170@gmail.com>
Change-Id: I45c640efd76cd59ed38d8d6e58d295020bac6bb2
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/109192
Reviewed-by: Miri Amarilio <mirilio@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Kevin Berry <kpberry@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/109268
Tested-by: He Gao <hegao@google.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>