selftests/bpf: Fix lsm_bdev dev_t encoding mismatch

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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: 96f4c251a0 ("selftests/bpf: add block device management selftests")
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Link: https://lore.kernel.org/bpf/20260720-selftests-bpf_fixes-v2-2-b450eda93dfe@suse.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

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Ricardo B. Marlière 2026-07-20 08:13:08 -03:00 • committed by Kumar Kartikeya Dwivedi

parent 0b236ac75d

commit 71cf3f3275

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tools/testing/selftests/bpf/prog_tests/lsm_bdev.c

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