bpf: Add MEM_WRITE attribute

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[ Upstream commit 6fad274f06 ]

Add a MEM_WRITE attribute for BPF helper functions which can be used in
bpf_func_proto to annotate an argument type in order to let the verifier
know that the helper writes into the memory passed as an argument. In
the past MEM_UNINIT has been (ab)used for this function, but the latter
merely tells the verifier that the passed memory can be uninitialized.

There have been bugs with overloading the latter but aside from that
there are also cases where the passed memory is read + written which
currently cannot be expressed, see also 4b3786a6c5 ("bpf: Zero former
ARG_PTR_TO_{LONG,INT} args in case of error").

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241021152809.33343-1-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Stable-dep-of: 8ea607330a ("bpf: Fix overloading of MEM_UNINIT's meaning")
Signed-off-by: Sasha Levin <sashal@kernel.org>

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This commit is contained in:

Daniel Borkmann 2024-10-21 17:28:05 +02:00 • committed by Greg Kroah-Hartman

parent d1100acab4

commit 8a33a047bd

6 changed files with 22 additions and 14 deletions

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14

include/linux/bpf.h

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10

kernel/bpf/helpers.c

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2

kernel/bpf/ringbuf.c

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2

kernel/bpf/syscall.c

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4

kernel/trace/bpf_trace.c

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4

net/core/filter.c

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