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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49808191ef9sm78066875e9.1.2026.08.01.09.52.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 01 Aug 2026 09:52:45 -0700 (PDT) Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Sat, 01 Aug 2026 18:52:45 +0200 Message-Id: Cc: , , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Eduard Zingerman" , "Martin KaFai Lau" , "Song Liu" , "Yonghong Song" , "Emil Tsalapatis" , "Jiri Olsa" , Subject: Re: [PATCH] fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions From: "Kumar Kartikeya Dwivedi" To: "Eric Biggers" , X-Mailer: aerc 0.21.0 References: <20260731003925.2728977-1-ebiggers@kernel.org> In-Reply-To: <20260731003925.2728977-1-ebiggers@kernel.org> On Fri Jul 31, 2026 at 2:39 AM CEST, Eric Biggers wrote: > The BPF verifier and the dynptr abstraction ensure that the memory space > referenced by a dynptr remains valid. They do not, however, provide any > guarantee that the contents of the memory are stable. kfuncs are > expected to remain memory-safe even if concurrent modifications occur. > > bpf_get_fsverity_digest() didn't follow that: it could crash if > arg->digest_size was concurrently modified. > > Fix that by using the known-good value hash_alg->digest_size instead. > This makes sense. > Also correctly handle sizes over INT_MAX, which previously caused an > integer overflow and crash. __bpf_dynptr_size() returns a u64. > I guess this occurs when using file dynptrs? Otherwise the size is capped t= o DYNPTR_SIZE_MASK. > Fixes: 67814c00de31 ("bpf, fsverity: Add kfunc bpf_get_fsverity_digest") > Cc: stable@vger.kernel.org > Signed-off-by: Eric Biggers > --- Acked-by: Kumar Kartikeya Dwivedi > [...]