bpf: Reject writes through untrusted BTF pointers

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check_ptr_to_btf_access() lets program-type btf_struct_access callbacks
validate writes before the default BTF access path rejects non-read
accesses. That bypasses the read-only policy for untrusted BTF pointers
created by helpers such as bpf_rdonly_cast().

Reject non-read accesses through PTR_UNTRUSTED BTF pointers at the
common entry point, before the callback branch to handle all cases.

Fixes: 282de143ea ("bpf: Introduce allocated objects support")
Signed-off-by: Nicholas Dudar <main.kalliope@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Reviewed-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>

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Nicholas Dudar 2026-07-08 05:07:50 +02:00 • committed by Eduard Zingerman

parent ee1bcf8271

commit ac65c710cc

1 changed files with 6 additions and 2 deletions

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kernel/bpf/verifier.c

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