netfilter: xt_tcpmss: check remaining length before reading optlen

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[ Upstream commit 735ee8582d ]

Quoting reporter:
  In net/netfilter/xt_tcpmss.c (lines 53-68), the TCP option parser reads
 op[i+1] directly without validating the remaining option length.

  If the last byte of the option field is not EOL/NOP (0/1), the code attempts
  to index op[i+1]. In the case where i + 1 == optlen, this causes an
  out-of-bounds read, accessing memory past the optlen boundary
  (either reading beyond the stack buffer _opt or the
  following payload).

Reported-by: sungzii <sungzii@pm.me>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Florian Westphal 2026-01-19 12:30:42 +01:00 • committed by Sasha Levin

parent 1c1a3de9bd

commit cd5beda7e0

1 changed files with 1 additions and 1 deletions

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net/netfilter/xt_tcpmss.c

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