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Tue, 05 May 2026 08:52:06 -0700 (PDT) Received: from plex ([71.181.43.54]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8fc2c91fb3bsm1353612585a.41.2026.05.05.08.52.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 May 2026 08:52:06 -0700 (PDT) Date: Tue, 5 May 2026 15:52:05 +0000 From: Pasha Tatashin To: Hugh Dickins , Baolin Wang , Andrew Morton , Jeff Xu , Kees Cook , Pratyush Yadav Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Brendan Jackman , Greg Thelen , stable@vger.kernel.org Subject: Re: [PATCH] memfd: deny writeable mappings when implying SEAL_WRITE Message-ID: References: <20260505133922.797635-1-pratyush@kernel.org> <177799542165.635180.17809433268620237886.b4-ty@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <177799542165.635180.17809433268620237886.b4-ty@soleen.com> X-Stat-Signature: abnow7pmdqiqpb4ihcfay75h8amjnhmb X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: B79941C0004 X-Rspam-User: X-HE-Tag: 1777996327-395513 X-HE-Meta: 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 5kTXRfIM 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 05-05 15:37, Pasha Tatashin wrote: > > On Tue, 05 May 2026 15:39:20 +0200, Pratyush Yadav wrote: > > When SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the > > implied seal is set after the check that makes sure the memfd can not > > have any writable mappings. This means one can use SEAL_EXEC to apply > > SEAL_WRITE while having writeable mappings. > > > > This breaks the contract that SEAL_WRITE provides and can be used by an > > attacker to pass a memfd that appears to be write sealed but can still > > be modified arbitrarily. > > > > [...] > > Applied, thanks! > > [1/1] memfd: deny writeable mappings when implying SEAL_WRITE > commit: 73f496662a9848021e75742a69a3239ea850c3ee ^^^ Please ignore, this should be Applied to MM tree. Pasha > > Best regards, > -- > Pasha Tatashin >