On 12/6/23 6:06 AM, Hou Tao wrote:
From: Hou Tao <houtao1@xxxxxxxxxx> When there is bpf_list_head or bpf_rb_root field in map value, the free of map btf and the free of map value may run concurrently and there may be use-after-free problem, so add two test cases to demonstrate it. The first test case tests the racing between the free of map btf and the free of array map. It constructs the racing by releasing the array map in the end after other ref-counter of map btf has been released. But it is still hard to reproduce the UAF problem, and I managed to reproduce it by queuing multiple kworkers to stress system_unbound_wq concurrently. The second case tests the racing between the free of map btf and the free of inner map. Beside using the similar method as the first one does, it uses bpf_map_delete_elem() to delete the inner map and to defer the release of inner map after one RCU grace period. The UAF problem can been easily reproduced by using bpf_next tree and a KASAN-enabled kernel.
Thanks, Hou. I will use your test cases as well during debugging besides my kernel mdeley() hack.
The reason for using two skeletons is to prevent the release of outer map and inner map in map_in_map_btf.c interfering the release of bpf map in normal_map_btf.c. Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> --- Hi, I was also working on the UAF problem caused by the racing between the free map btf and the free map value. However considering Yonghong posted the patch first [1], I decided to post the selftest for the problem. The reliable reproduce of the problem depends on the "Fix the release of inner map" patch-set in bpf-next. [1]: https://lore.kernel.org/bpf/20231205224812.813224-1-yonghong.song@xxxxxxxxx/ .../selftests/bpf/prog_tests/map_btf.c | 88 +++++++++++++++++++ .../selftests/bpf/progs/map_in_map_btf.c | 73 +++++++++++++++ .../selftests/bpf/progs/normal_map_btf.c | 56 ++++++++++++ 3 files changed, 217 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/map_btf.c create mode 100644 tools/testing/selftests/bpf/progs/map_in_map_btf.c create mode 100644 tools/testing/selftests/bpf/progs/normal_map_btf.c
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