bpf: fix sanitation of alu op with pointer / scalar type from different paths

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[ commit d3bd7413e0 upstream ]

While 979d63d50c ("bpf: prevent out of bounds speculation on pointer
arithmetic") took care of rejecting alu op on pointer when e.g. pointer
came from two different map values with different map properties such as
value size, Jann reported that a case was not covered yet when a given
alu op is used in both "ptr_reg += reg" and "numeric_reg += reg" from
different branches where we would incorrectly try to sanitize based
on the pointer's limit. Catch this corner case and reject the program
instead.

Fixes: 979d63d50c ("bpf: prevent out of bounds speculation on pointer arithmetic")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Daniel Borkmann 2019-01-28 21:23:29 +01:00 • committed by Greg Kroah-Hartman

parent 078da99d44

commit 4bce22c364

2 changed files with 49 additions and 13 deletions

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include/linux/bpf_verifier.h

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61

kernel/bpf/verifier.c

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