bpf: track immediate values written to stack by BPF_ST instruction

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For aligned stack writes using BPF_ST instruction track stored values
in a same way BPF_STX is handled, e.g. make sure that the following
commands produce similar verifier knowledge:

  fp[-8] = 42;             r1 = 42;
                       fp[-8] = r1;

This covers two cases:
 - non-null values written to stack are stored as spill of fake
   registers;
 - null values written to stack are stored as STACK_ZERO marks.

Previously both cases above used STACK_MISC marks instead.

Some verifier test cases relied on the old logic to obtain STACK_MISC
marks for some stack values. These test cases are updated in the same
commit to avoid failures during bisect.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20230214232030.1502829-2-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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This commit is contained in:

Eduard Zingerman 2023-02-15 01:20:27 +02:00 • committed by Alexei Starovoitov

parent 62d101d5f4

commit ecdf985d76

2 changed files with 80 additions and 48 deletions

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18

kernel/bpf/verifier.c

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110

tools/testing/selftests/bpf/verifier/bounds_mix_sign_unsign.c

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