netfilter: nftables: exthdr: fix 4-byte stack OOB write

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[ Upstream commit fd94d9dade ]

If priv->len is a multiple of 4, then dst[len / 4] can write past
the destination array which leads to stack corruption.

This construct is necessary to clean the remainder of the register
in case ->len is NOT a multiple of the register size, so make it
conditional just like nft_payload.c does.

The bug was added in 4.1 cycle and then copied/inherited when
tcp/sctp and ip option support was added.

Bug reported by Zero Day Initiative project (ZDI-CAN-21950,
ZDI-CAN-21951, ZDI-CAN-21961).

Fixes: 49499c3e6e ("netfilter: nf_tables: switch registers to 32 bit addressing")
Fixes: 935b7f6430 ("netfilter: nft_exthdr: add TCP option matching")
Fixes: 133dc203d7 ("netfilter: nft_exthdr: Support SCTP chunks")
Fixes: dbb5281a1f ("netfilter: nf_tables: add support for matching IPv4 options")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Florian Westphal 2023-09-05 23:13:56 +02:00 • committed by Greg Kroah-Hartman

parent 6cf0d1d5a5

commit d9ebfc0f21

1 changed files with 14 additions and 8 deletions

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net/netfilter/nft_exthdr.c

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