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[34.127.51.67]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2df6a516d58sm24409255ad.11.2026.09.24.03.00.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Sep 2026 03:00:22 -0700 (PDT) From: Hui Peng To: gregkh@linuxfoundation.org, arve@android.com, tkjos@android.com, maco@android.com, brauner@kernel.org, cmllamas@google.com Cc: maco@google.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Hui Peng Subject: [PATCH v2 2/2] binder: free transaction buffer via binder_free_buf() on read -EFAULT Date: Thu, 24 Sep 2026 10:00:19 +0000 Message-ID: <20260924100019.3389555-3-benquike@gmail.com> X-Mailer: git-send-email 2.56.0.rc1.310.g51773c2048-goog In-Reply-To: <20260919213650.3316812-1-benquike@gmail.com> References: <20260919213650.3316812-1-benquike@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In binder_thread_read(), if put_user() or copy_to_user() returns -EFAULT, the failure paths call binder_cleanup_transaction() without setting t->buffer->transaction = NULL or calling binder_free_buf(proc, thread, buffer, true). Because allow_user_free remains 0, the binder_buffer and all translated binder_node / binder_ref references inside it are permanently leaked. For oneway transactions (TF_ONE_WAY), node->has_async_transaction remains true forever, wedging all subsequent async transactions to that node. Fix this by setting buffer->transaction = NULL and calling binder_free_buf(proc, thread, buffer, true) on put_user() / copy_to_user() -EFAULT errors in binder_thread_read(). Tested in QEMU against Linux 7.3.0-rc3 using a multi-process C reproducer: triggering copy_to_user() failure on a one-way transaction: on the unfixed kernel, binder_cleanup_transaction() leaked the transaction buffer and left node->has_async_transaction set to true (wedging subsequent async transactions); whereas with this fix applied, binder_free_buf() is called on -EFAULT, clearing buffer->transaction and freeing the allocation cleanly. Fixes: 44d8047f1d87 ("binder: use standard functions to allocate fds") Cc: stable@vger.kernel.org Reviewed-by: Carlos Llamas Assisted-by: LLM Signed-off-by: Hui Peng --- Changes in v2: - Split out as patch 2/2 as requested by Greg Kroah-Hartman and Carlos Llamas. - Added QEMU test procedure details in commit message body. - Added Reviewed-by tag from Carlos Llamas. drivers/android/binder.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index ee01e6a06631..efff59853752 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -5127,24 +5128,32 @@ static int binder_thread_read(struct binder_proc *proc, trsize = sizeof(tr); } if (put_user(cmd, (uint32_t __user *)ptr)) { + struct binder_buffer *buffer = t->buffer; + if (t_from) binder_thread_dec_tmpref(t_from); + buffer->transaction = NULL; binder_cleanup_transaction(t, "put_user failed", BR_FAILED_REPLY); + binder_free_buf(proc, thread, buffer, true); return -EFAULT; } ptr += sizeof(uint32_t); if (copy_to_user(ptr, &tr, trsize)) { + struct binder_buffer *buffer = t->buffer; + if (t_from) binder_thread_dec_tmpref(t_from); + buffer->transaction = NULL; binder_cleanup_transaction(t, "copy_to_user failed", BR_FAILED_REPLY); + binder_free_buf(proc, thread, buffer, true); return -EFAULT; } ptr += trsize;