bpf: Correct the overflow check comment in bpf_iter_num_next()

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The comment on the s->cur + 1 >= s->end check claims the (s64) cast is
needed to avoid overflow when s->cur == s->end == INT_MAX. It isn't:
s->cur + 1 is computed in int and wraps before the cast, so the cast
changes nothing (INT_MAX + 1 compares the same either way).

The wraparound is the point. bpf_iter_num_new() sets s->cur = start - 1,
which wraps to INT_MAX for start == INT_MIN, and the wrapping s->cur + 1
brings it back to start. (s64)s->cur + 1 would instead break iterators
starting at INT_MIN.

Drop the cast and reword the comment. No functional change; the wrap is
well-defined under -fno-strict-overflow.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260804134601.2305303-2-puranjay@kernel.org

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Puranjay Mohan 2026-08-04 06:45:53 -07:00 • committed by Andrii Nakryiko

parent 363b15d855

commit 8efd87051c

1 changed files with 4 additions and 5 deletions

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kernel/bpf/bpf_iter.c

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