From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Florian Westphal <fw@strlen.de>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: [PATCH nft] evaluate: fix expression data corruption
Date: Wed, 12 Mar 2025 01:14:59 +0100 [thread overview]
Message-ID: <Z9DSA-cH-eWPyWBK@calendula> (raw)
In-Reply-To: <20250311130707.12512-1-fw@strlen.de>
On Tue, Mar 11, 2025 at 02:07:03PM +0100, Florian Westphal wrote:
> Sometimes nftables will segfault when doing error-unwind of the included
> afl-generated bogon.
>
> The problem is the unconditional write access to expr->set_flags in
> expr_evaluate_map():
>
> mappings->set_flags |= NFT_SET_MAP;
>
> ... but mappings can point to EXPR_VARIABLE (legal), where this will flip
> a bit in unused, but allocated memory (i.e., has no effect).
>
> In case of the bogon, mapping is EXPR_RANGE_SYMBOL, and the store can flip
> a bit in identifier_range[1], this causes crash when the pointer is freed.
>
> We can't use expr->set_flags unconditionally, so rework this to pass
> set_flags as argument and place all read and write accesses in places where
> we've made sure we are dealing with EXPR_SET.
>
> Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>
prev parent reply other threads:[~2025-03-12 0:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-11 13:07 [PATCH nft] evaluate: fix expression data corruption Florian Westphal
2025-03-12 0:14 ` Pablo Neira Ayuso [this message]
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