bpf: fix integer overflows

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There were various issues related to the limited size of integers used in
the verifier:
 - `off + size` overflow in __check_map_access()
 - `off + reg->off` overflow in check_mem_access()
 - `off + reg->var_off.value` overflow or 32-bit truncation of
   `reg->var_off.value` in check_mem_access()
 - 32-bit truncation in check_stack_boundary()

Make sure that any integer math cannot overflow by not allowing
pointer math with large values.

Also reduce the scope of "scalar op scalar" tracking.

Fixes: f1174f77b5 ("bpf/verifier: rework value tracking")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

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Alexei Starovoitov 2017-12-18 20:12:00 -08:00 • committed by Daniel Borkmann

parent 179d1c5602

commit bb7f0f989c

2 changed files with 50 additions and 2 deletions

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4

include/linux/bpf_verifier.h

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48

kernel/bpf/verifier.c

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