This patch-set modifies BPF verifier to accept programs that read from uninitialized stack locations, but only if executed in privileged mode. This provides significant verification performance gains: 30% to 70% less processed states for big number of test programs. The reason for performance gains comes from treating STACK_MISC and STACK_INVALID as compatible, when cached state is compared to current state in verifier.c:stacksafe(). The change should not affect safety, because any value read from STACK_MISC location has full binary range (e.g. 0x00-0xff for byte-sized reads). Details and measurements are provided in the description for the patch #1. The change was suggested by Andrii Nakryiko, the initial patch was created by Alexei Starovoitov. The discussion could be found at [1]. Changes v1 -> v2 (v1 available at [2]): - Calls to helper functions now convert STACK_INVALID to STACK_MISC (suggested by Andrii); - The test case progs/test_global_func10.c is updated to expect new error message. Before recent commit [3] exact content of error messages was not verified for this test. - Replaced incorrect '//'-style comments in test case asm blocks by '/*...*/'-style comments in order to fix compilation issues; - Changed the tag from "Suggested-By" to "Co-developed-by" for Alexei on patch #1, please let me know if this is appropriate use of the tag. [1] https://lore.kernel.org/bpf/CAADnVQKs2i1iuZ5SUGuJtxWVfGYR9kDgYKhq3rNV+kBLQCu7rA@xxxxxxxxxxxxxx/ [2] https://lore.kernel.org/bpf/20230216183606.2483834-1-eddyz87@xxxxxxxxx/ [3] 95ebb376176c ("selftests/bpf: Convert test_global_funcs test to test_loader framework") Eduard Zingerman (2): bpf: Allow reads from uninit stack selftests/bpf: Tests for uninitialized stack reads kernel/bpf/verifier.c | 11 +- .../selftests/bpf/prog_tests/uninit_stack.c | 9 ++ .../selftests/bpf/progs/test_global_func10.c | 8 +- .../selftests/bpf/progs/uninit_stack.c | 87 +++++++++++++++ tools/testing/selftests/bpf/verifier/calls.c | 13 ++- .../bpf/verifier/helper_access_var_len.c | 104 ++++++++++++------ .../testing/selftests/bpf/verifier/int_ptr.c | 9 +- .../selftests/bpf/verifier/search_pruning.c | 13 ++- tools/testing/selftests/bpf/verifier/sock.c | 27 ----- .../selftests/bpf/verifier/spill_fill.c | 7 +- .../testing/selftests/bpf/verifier/var_off.c | 52 --------- 11 files changed, 204 insertions(+), 136 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/uninit_stack.c create mode 100644 tools/testing/selftests/bpf/progs/uninit_stack.c -- 2.39.1
