bpf: mark a NULL memory argument of a call precise

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check_mem_reg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

The argument may live on the stack rather than in a register when a
call has more than MAX_BPF_FUNC_REG_ARGS arguments, hence the new
mark_arg_precision() helper.

Fixes: e5069b9c23 ("bpf: Support pointers in global func args")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-3-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Eduard Zingerman 2026-09-04 17:05:54 -07:00 • committed by Alexei Starovoitov

parent 593c8eb0fb

commit f1e418129f

1 changed files with 10 additions and 1 deletions

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kernel/bpf/verifier.c

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