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Arthur Fabre authored
bpf_sk_storage maps use multiple spin locks to reduce contention. The number of locks to use is determined by the number of possible CPUs. With only 1 possible CPU, bucket_log == 0, and 2^0 = 1 locks are used. When updating elements, the correct lock is determined with hash_ptr(). Calling hash_ptr() with 0 bits is undefined behavior, as it does: x >> (64 - bits) Using the value results in an out of bounds memory access. In my case, this manifested itself as a page fault when raw_spin_lock_bh() is called later, when running the self tests: ./tools/testing/selftests/bpf/test_verifier 773 775 [ 16.366342] BUG: unable to handle page fault for address: ffff8fe7a66f93f8 Force the minimum number of locks to two. Signed-off-by:
Arthur Fabre <afabre@cloudflare.com> Fixes: 6ac99e8f ("bpf: Introduce bpf sk local storage") Acked-by:
Andrii Nakryiko <andriin@fb.com> Signed-off-by:
Alexei Starovoitov <ast@kernel.org>
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