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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Hwhsj8kN; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4D763606A31E; Mon, 26 Oct 2026 21:08:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Hwhsj8kN Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B4DF1F01828; Mon, 26 Oct 2026 21:08:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793048908; bh=aZY6emueEsceME7nXNq6gUfKhqrQcT2cFezDIABkUGw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Hwhsj8kNM/003xoVUCIY6kkGhTMwCG7vilt/Dph6Rs2EcwYc9BgMFYtM3gSdCLUv4 I+tMEzKtq5KAbamFFvZx7+ti1rXjRJsMZjvz0qerVCMxXjC93hhuyyMUiLAmtzc1/W LR4Z/+Pq0jLyAo39zmyDSxqVjNIeiDuZTxpYCVfdxa8mhWwNuCyhOz1ppbvUAknygE 3GYifpJYvEc3MVOEyQZ5/oL5Xo0WCWkoroRzPUaoRpTDIFj7D2vLbekCufU0BWV8ka oeA1q6H6o0L+DLOpROZC2NULQUuPdxHZ3YYT75nxwHQAPF+Dr37k+z7MxY7tkjCqzh wc8fUODq2yO1Q== Message-ID: <5d441cff-ef78-4bdf-b727-9eb697ca7478@kernel.org> Date: Mon, 26 Oct 2026 22:08:16 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hugetlbfs: enforce F_SEAL_EXEC on chmod To: Samiullah Khawaja , Andrew Morton , Muchun Song , Oscar Salvador Cc: Jeff Xu , Daniel Verkamp , David Matlack , Pasha Tatashin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261026205555.2918396-1-skhawaja@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/26/26 21:55, Samiullah Khawaja wrote: > F_SEAL_EXEC prevents the exec bits of a memfd from being changed once > the seal has been set. F_SEAL_EXEC is included in F_ALL_SEALS, so > userspace can set it with F_ADD_SEALS on hugetlbfs memfds just like on > shmem memfds, and F_GET_SEALS then reports it as set. However, the check > that rejects the mode change was only added to shmem_setattr(). > hugetlbfs_setattr() never looks at the seal, so the owner of a sealed > hugetlbfs memfd can still make it executable with chmod(). For the same > reason, MFD_NOEXEC_SEAL provides no guarantee when it is combined with > MFD_HUGETLB. > > The memfd selftest already covers this, but only the shmem run passes. > When run as "memfd_test hugetlbfs", the test aborts in SEAL-EXEC because > fchmod() succeeds on a sealed file, and none of the remaining tests are > executed. > > Add the same check to hugetlbfs_setattr() that shmem_setattr() has, so > that a mode change touching the exec bits fails with -EPERM while > F_SEAL_EXEC is set. > > Fixes: 6fd7353829ca ("mm/memfd: add F_SEAL_EXEC") > Cc: stable@vger.kernel.org > Signed-off-by: Samiullah Khawaja > --- > fs/hugetlbfs/inode.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 01c4d6f44ebe..56e0588d295d 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -842,6 +842,10 @@ static int hugetlbfs_setattr(const struct mnt_idmap *idmap, > > trace_hugetlbfs_setattr(inode, dentry, attr); > > + if ((info->seals & F_SEAL_EXEC) && (ia_valid & ATTR_MODE) && > + ((inode->i_mode ^ attr->ia_mode) & 0111)) > + return -EPERM; > + > if (ia_valid & ATTR_SIZE) { > loff_t oldsize = inode->i_size; > loff_t newsize = attr->ia_size; > > base-commit: f1ac44c32cba88ad65dcecd4a279661d14e93651 https://lore.kernel.org/r/20261026-fixes_shmem-v1-5-703206d5fa0c@kernel.org -- Cheers, David