bpf: Check global subprog exception paths

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Global subprogs are verified independently and are not descended into
when their callers are symbolically executed. This means a caller can
hold references or locks across a global subprog call that may throw,
while the verifier only checks the non-exceptional return path at the
call site.

Record whether a subprog might throw in the CFG summary pass, alongside
the existing might_sleep and packet-data-changing summaries, and
propagate that effect through reachable callees.

When a global subprog is marked as possibly throwing, push the normal
continuation and validate the exceptional path immediately at the call
site, avoiding a synthetic exception state and associated special case
in the pruning checks.

Fixes: f18b03faba ("bpf: Implement BPF exceptions")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260517075530.3461166-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Kumar Kartikeya Dwivedi 2026-05-17 09:55:28 +02:00 • committed by Alexei Starovoitov

parent a828abbb89

commit 3d562d35a0

3 changed files with 31 additions and 7 deletions

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2

include/linux/bpf_verifier.h

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13

kernel/bpf/cfg.c

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23

kernel/bpf/verifier.c

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