From 71cf3f3275e5f4d7f31bd540608c80535343b427 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ricardo=20B=2E=20Marli=C3=A8re?= Date: Mon, 20 Jul 2026 08:13:08 -0300 Subject: [PATCH] selftests/bpf: Fix lsm_bdev dev_t encoding mismatch MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit progs/lsm_bdev.c keys its verity_devices hashmap with the raw kernel dev_t read straight off bdev->bd_dev, i.e. MKDEV(major, minor) = (major << 20) | minor. prog_tests/lsm_bdev.c instead builds its lookup key with dev_key = (__u32)st.st_rdev from stat(2), but the stat(2) syscall fills st_rdev via the kernel's new_encode_dev(), a different bit layout: (minor & 0xff) | (major << 8) | ((minor & ~0xff) << 12). For any device with a non-trivial major these two values differ, so the lookup can never find what the BPF program stored, and test_lsm_bdev() always fails with: test_lsm_bdev:FAIL:map lookup unexpected error: -2 (errno 2) Reconstruct the raw kernel dev_t from the decoded major/minor instead of casting st_rdev directly, restoring the layout the BPF program actually reads. Fixes: 96f4c251a087 ("selftests/bpf: add block device management selftests") Signed-off-by: Ricardo B. Marlière Acked-by: Ihor Solodrai Link: https://lore.kernel.org/bpf/20260720-selftests-bpf_fixes-v2-2-b450eda93dfe@suse.com Signed-off-by: Kumar Kartikeya Dwivedi --- tools/testing/selftests/bpf/prog_tests/lsm_bdev.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/prog_tests/lsm_bdev.c b/tools/testing/selftests/bpf/prog_tests/lsm_bdev.c index a970798e1173..28bc4b117f41 100644 --- a/tools/testing/selftests/bpf/prog_tests/lsm_bdev.c +++ b/tools/testing/selftests/bpf/prog_tests/lsm_bdev.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include #include "lsm_bdev.skel.h" @@ -172,7 +173,7 @@ void test_lsm_bdev(void) if (!ASSERT_OK(stat(DM_DEV_PATH, &st), "stat dm dev")) goto remove_dm; - dev_key = (__u32)st.st_rdev; + dev_key = (major(st.st_rdev) << 20) | minor(st.st_rdev); /* Look up the device in the BPF map and verify. */ err = bpf_map__lookup_elem(skel->maps.verity_devices,