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AJvYcCWMoJjJfVbMaD3APtno8goEnFJIcX2pnp6kHF+5vo2DCkw8yXDm1umpFGD+ZHxmKyJ68kwkdTuYhg==@kvack.org X-Gm-Message-State: AOJu0YxnSx2/n/SE2bVHQux/wdrrFq3zEb9n9pPXG5Ackm7N8NK7o0oi A/56KJsY75Oygcg4YZEDfzG05cMzk9ycd2VNih/Cxj6oiaUUndK5NUMVeS62p2BRTWqMmb1ab3P k53o3dPwl5QnAUqqIGA== X-Received: from wrnc10.prod.google.com ([2002:adf:e74a:0:b0:437:6b00:8cbc]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:240e:b0:431:808:2d50 with SMTP id ffacd0b85a97d-4379db24fb0mr20850357f8f.13.1771338176111; Tue, 17 Feb 2026 06:22:56 -0800 (PST) Date: Tue, 17 Feb 2026 14:22:39 +0000 In-Reply-To: <20260217-binder-vma-check-v1-0-1a2b37f7b762@google.com> Mime-Version: 1.0 References: <20260217-binder-vma-check-v1-0-1a2b37f7b762@google.com> X-Developer-Key: i=aliceryhl@google.com; a=openpgp; fpr=49F6C1FAA74960F43A5B86A1EE7A392FDE96209F X-Developer-Signature: v=1; a=openpgp-sha256; l=2851; i=aliceryhl@google.com; h=from:subject:message-id; bh=Efrfc+ezEwByI/gNWdWXysiNKRrRQRbM6CMnAM/EeeM=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBplHm5prYIkklTAyDnHpvdtT4ZnH/PWKGUlo9A7 e0m3cQkth6JAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCaZR5uQAKCRAEWL7uWMY5 RjRCD/9Hw/hm2Xm3vaKkplhmlEb0PY2QkvIEUCwKHyT/1GELqXg87R/lLUOS5SfbeX6FB3MKzyZ qMQrby2qSbni8YHedTtzjFZZNS5kKbyOIXtkyiK0htiI4E+oV637qnqGzSqId3M9Sc1FbgYhZmD M5ot3f02kV1P9LLybjMEAXBxuEgYKjHv/Cdc1tan0KELqEmRyXF7wneln2hM9GGoXaXeUrk6/EW aDQo1JuVycWlZgzXY1bfMUCYbABcHl1xVcVt6+HAfCHpTPleAIvy1xFDoNtMUB//NwUT3ne7AjJ XodQxTZxTZZqsD2QSBzk+b6i8yJRFv9EVxBEFHn5N/F5PsPv2/HYU1eXWe6X7oh6UBFkeOHE/g9 wQ2Xt4wa7HWgQwUYEofVqhJwcadiMbw9NAuB5ghDBrEZoprpr5Gg6zyYq6FbuJU9l5vWTKgarOb /5rddyZlLCgqDppocuz5wInoSxvJkpVwSwk10MjRSIyyURCpZtFQ2m2HDTqhYP5pgc8UQ1Ke5Nh 8XFyDEqHwCRFMaxZ8ZaGWp4OFfAPKVJXkBPqToS90XrexsvF6L9m7Nhq5qSIejoh0JLBvUzILyQ XxBk0KpMUnllvaBB7ZXdoilUxvFY1GS5qS29U3uVRQcjiFtOdMyTifisrClGZ3F/2bpSewTI7f3 mliJbE3uEwn0XCg== X-Mailer: b4 0.14.2 Message-ID: <20260217-binder-vma-check-v1-2-1a2b37f7b762@google.com> Subject: [PATCH 2/2] rust_binder: avoid reading the written value in offsets array From: Alice Ryhl To: Greg Kroah-Hartman , Carlos Llamas , Jann Horn Cc: Miguel Ojeda , Boqun Feng , Gary Guo , "=?utf-8?q?Bj=C3=B6rn_Roy_Baron?=" , Benno Lossin , Andreas Hindborg , Trevor Gross , Danilo Krummrich , Lorenzo Stoakes , "Liam R. Howlett" , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-mm@kvack.org, Alice Ryhl , stable@vger.kernel.org Content-Type: text/plain; charset="utf-8" X-Rspamd-Server: rspam09 X-Stat-Signature: r1ho7smn5w9cwh9sygq7zix968w37zac X-Rspamd-Queue-Id: 0486F1A000C X-Rspam-User: X-HE-Tag: 1771338177-600576 X-HE-Meta: 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 vEiWhMZg Rjqsh9PsBONuwtc6jl7+6TGtUfJhrGUENAnBtqBM9nadIrnuFYOpeD73Reom3/zeUPlW2Gh/JnbxlU1nvdF+Hy/z9zvj1MiDrbHS1No9W48R0E0WahMvV1XQAMEUpqK2abRgJGtPjk6TV1QP7axMI4yHKOVgqyOYnCr3q+YrU3Od0BZJLhSy8bZU1JZ3F5YD3JSw4RJHN+ftW0ODQ2qSK4WwaU6NoksD+azu3k3q6Hv8qnP7HpQqvWM0AOQ8L06er7f17YsVhxYS7yKTPogq51wOhgIrw5SUb2GzDdySvlTOurq0d/bEWTWg5xqqtTn8L2wpDQMRTkBU7UxM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When sending a transaction, its offsets array is first copied into the target proc's vma, and then the values are read back from there. This is normally fine because the vma is a read-only mapping, so the target process cannot change the value under us. However, if the target process somehow gains the ability to write to its own vma, it could change the offset before it's read back, causing the kernel to misinterpret what the sender meant. If the sender happens to send a payload with a specific shape, this could in the worst case lead to the receiver being able to privilege escalate into the sender. The intent is that gaining the ability to change the read-only vma of your own process should not be exploitable, so remove this TOCTOU read even though it's unexploitable without another Binder bug. Cc: stable@vger.kernel.org Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver") Reported-by: Jann Horn Signed-off-by: Alice Ryhl --- drivers/android/binder/thread.rs | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-) diff --git a/drivers/android/binder/thread.rs b/drivers/android/binder/thread.rs index 1f1709a6a77abc1c865cc9387e7ba7493448c71d..f58ecccf5bb10a4b916d14a38dbb3bdfdda24ff8 100644 --- a/drivers/android/binder/thread.rs +++ b/drivers/android/binder/thread.rs @@ -1016,12 +1016,9 @@ pub(crate) fn copy_transaction_data( // Copy offsets if there are any. if offsets_size > 0 { - { - let mut reader = - UserSlice::new(UserPtr::from_addr(trd_data_ptr.offsets as _), offsets_size) - .reader(); - alloc.copy_into(&mut reader, aligned_data_size, offsets_size)?; - } + let mut offsets_reader = + UserSlice::new(UserPtr::from_addr(trd_data_ptr.offsets as _), offsets_size) + .reader(); let offsets_start = aligned_data_size; let offsets_end = aligned_data_size + offsets_size; @@ -1042,11 +1039,9 @@ pub(crate) fn copy_transaction_data( .step_by(size_of::()) .enumerate() { - let offset: usize = view - .alloc - .read::(index_offset)? - .try_into() - .map_err(|_| EINVAL)?; + let offset = offsets_reader.read::()?; + view.alloc.write(index_offset, &offset)?; + let offset: usize = offset.try_into().map_err(|_| EINVAL)?; if offset < end_of_previous_object || !is_aligned(offset, size_of::()) { pr_warn!("Got transaction with invalid offset."); -- 2.53.0.273.g2a3d683680-goog