From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f179.google.com (mail-pf1-f179.google.com [209.85.210.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4CCA041DDEE for ; Fri, 7 Aug 2026 10:12:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786097548; cv=none; b=HzDuaoSkWAEJ57M6KsORf2k1msnLPw9aJqxxDJNKz2Fph1PFBKZ5xXPNnfAsQzSwxf10Qm9IsMdHHLFWb2Pp4NZPZTuYhN6BvU9uXYyZbmxT0Bbo9w6xBA0K0lPj+z3o/gYVmBzM1wjpI62xuZe8JRMkmiOndNsK7HeM1z5J8SY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786097548; c=relaxed/simple; bh=F1UzQeZHsiabgRSoKYgZ6x2SoQv1aOF17+66tpxhGm8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Avk3R+OImv84DiEJXBJ4ySABdPE2f9n2Dl/SXduGooIVgHVVt5tHpjqTDKLfAl/9Jop1/EmFUaJMT6N1iGLuvy6hNE52JhuHi/LUUlWatkudy8NDhZF31vhTRjv5GGcGwLRo+vieUZ8Nh7ZgyifjkYnOk0FVJa0FUUKivPACh54= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=R+UAkjmY; arc=none smtp.client-ip=209.85.210.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="R+UAkjmY" Received: by mail-pf1-f179.google.com with SMTP id d2e1a72fcca58-848743155bcso1559560b3a.0 for ; Fri, 07 Aug 2026 03:12:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1786097547; x=1786702347; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=b1QPAle4B6UVEoKy/UvltvjtFmYUt6krDcEVyTwixgM=; b=R+UAkjmYQVwAFPG/XsDDKTicbg2ber+BJXst4QUEEcglLGxzmaLZ2eh70Ke6b39D8n gNTdaRXw0hOTbc227iBaKwE0rt3YGJPj2pMchuFwTJyXiBooqyBuCiSAaSIxokSu7g3D ND9NDcZsi2087K4qhwpt4iOa83ns5uvjgIspETrhX/hUrsjSqx0KmTgFSWrWYmf6jwNF c4xQQsarmmL2nBp/0G+ALhmfUEhTLKeb5YixerbyXVC93ge0iIiQbyBOgD9/0zhTQcT8 cFQ5tTqb2Rug+fb2JNyaQueDucVoveEQs+UmBupD2qshTb065ALYnOin/Uo30LUu1s00 LvTw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786097547; x=1786702347; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=b1QPAle4B6UVEoKy/UvltvjtFmYUt6krDcEVyTwixgM=; b=gInpmQL2QbYzzvEeorJtCYN1l0G0NmHdli0tipxvsIIK9dX4y/Gqf0bztUqK3Sn+Sb Oa/gyOkdVieMkXb2XX0E4K4tJmiigkCTMywyhXjctisvKH+WeUGRw0PbkLIQGGCjSAud AaWfyk+k7NLehBEFU/OHJFLCOIDIZrM4T1f59jQ1qElJ8s7+7oNg4jKY++hCw+UX5bl0 YB1YDIpApE3hX0/rPzKWpm+t09YukZa3QP5o6igw+iqzOm/vMMZ63YV1/DWG7YLLMd6E JGZBjol5/Lrbp8aW+a2lmqnf1f/hmgf8ouhrDC/4voT5fzuWaTIJUyGHkzAlCY9+QQ4q ABMw== X-Forwarded-Encrypted: i=1; AHgh+RpS+YsxFjMwxVb5xnejM9mHT78wwLxGJ+5W0uOnWwCKbEIC2GUuPr0X0iKsRsYC2QUV2sw25FcCahh0ZQ==@vger.kernel.org X-Gm-Message-State: AOJu0Yw2SR8l5vw4sD/4SmH3TTpWmEysu2b6XmYnGdrq5oE8M5icM+EE vFF/vwBSWgfeGRUWppW2sTvw4kEe/4B6MvMH+qh8KEJCv6CM2yTImnwr X-Gm-Gg: AR+sD13poLblfds343lfWIZmxWJqt42jCmpm8eAKBYVtlEGW3+QPl01XSP9IUA5+kZa 5X2PeAP7YRqaS/pr5IgOLftwglZEw2FZpVQWc856x817QbKb7ZwcvU+nuEz0V+RTBmIBgaiT+tL j+MOAE9HlYemjM56ExyEYjkxp7tKIkRMWYbpHq5Qc//kfAQljuj3/JOt0MEtEkZZepX3IHn6XXE 54eSAAIYmhg6EopWtTJnpPx8HzI6u/VchUvNXa/mpqRilU6xJlm8+0P2V5z3wzHvTZH81yt0GZ8 K7q9ttA1j5+FzFfXQmr9hNufL6IdfgCbiQLuVxluVKoDMp+LbobNVb5OPCer7Z3uwgPRiMnjRmL vNPQObSuV1H1eKvSAaIXxWqceaxywWDvng2aIrk1eFH1lzVkgEWzAkZJOBqdKJqfFSrkg0j1tQn 5lbaccvZ02bYgcYexQ44wLAb0IqZrjB97jzmXdScTpyOEhhbfw/fQ9HGvtuy3JdEz/ X-Received: by 2002:a05:6a00:ba06:b0:84d:ff47:fa53 with SMTP id d2e1a72fcca58-84f4fd9f842mr10114159b3a.2.1786097546501; Fri, 07 Aug 2026 03:12:26 -0700 (PDT) Received: from baineng-pc.. ([117.133.183.252]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84f5a5528adsm797510b3a.45.2026.08.07.03.12.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Aug 2026 03:12:26 -0700 (PDT) From: Baineng Shou To: Sumit Semwal , =?UTF-8?q?Christian=20K=C3=B6nig?= , "T . J . Mercier" , Benjamin Gaignard , Brian Starkey , John Stultz , Sandeep Patil , "Andrew F . Davis" , Srinivas Kandagatla , David Airlie , Simona Vetter Cc: stable@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Baineng Shou Subject: [PATCH v6 4/4] selftests: dmabuf-heaps: add fd-leak-on-EFAULT regression test Date: Fri, 7 Aug 2026 18:11:40 +0800 Message-Id: <20260807101140.1357218-5-shoubaineng@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260807101140.1357218-1-shoubaineng@gmail.com> References: <20260807101140.1357218-1-shoubaineng@gmail.com> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add a test case that verifies no file descriptor is leaked when DMA_HEAP_IOCTL_ALLOC succeeds internally but copy_to_user() fails to deliver the fd number back to userspace. The failure is triggered by placing the ioctl argument in a private anonymous page and flipping it to PROT_READ (via mprotect) between the kernel's copy_from_user() and copy_to_user() calls. With the buggy kernel the ioctl returns -EFAULT but leaves an extra open fd in the process's fd table; with the fixed kernel the fd count is unchanged. This serves as a regression test for: "dma-buf: dma-heap: don't publish fd before copy_to_user() succeeds" Suggested-by: Sumit Semwal Signed-off-by: Baineng Shou --- .../selftests/dmabuf-heaps/dmabuf-heap.c | 113 +++++++++++++++++- 1 file changed, 112 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/dmabuf-heaps/dmabuf-heap.c b/tools/testing/selftests/dmabuf-heaps/dmabuf-heap.c index fc9694fc4e89..1d49df671919 100644 --- a/tools/testing/selftests/dmabuf-heaps/dmabuf-heap.c +++ b/tools/testing/selftests/dmabuf-heaps/dmabuf-heap.c @@ -390,6 +390,116 @@ static void test_alloc_errors(char *heap_name) close(heap_fd); } +/* + * count_open_fds - return the number of open file descriptors. + * + * The fd opened by opendir() itself is counted, but since it is opened + * and closed within each call, it cancels out when comparing two counts. + * Returns -1 on error. + */ +static int count_open_fds(void) +{ + DIR *d = opendir("/proc/self/fd"); + struct dirent *de; + int count = 0; + + if (!d) + return -1; + + while ((de = readdir(d))) + if (de->d_name[0] != '.') + count++; + closedir(d); + return count; +} + +/* + * test_alloc_no_fd_leak_on_efault - verify no fd is leaked when + * copy_to_user() fails during DMA_HEAP_IOCTL_ALLOC. + * + * The bug: dma_buf_fd() called fd_install() before copy_to_user(). + * If copy_to_user() then failed (e.g. via mprotect), the fd was + * silently installed in the fd table but never returned to userspace. + * + * The fix: reserve the fd with get_unused_fd_flags() first, attempt + * copy_to_user(), and only call fd_install() on success. + * + * We trigger the failure by placing the ioctl argument in a private + * anonymous page and flipping it to PROT_READ before the ioctl. + * Inside the kernel, copy_from_user() reads from the page (reads are + * allowed under PROT_READ, so it succeeds), but copy_to_user() that + * writes the fd number back faults, returning -EFAULT. We then + * count open file descriptors before and after; with the bug an extra + * fd is left in the table. + */ +static void test_alloc_no_fd_leak_on_efault(char *heap_name) +{ + int heap_fd = -1; + int fd_before, fd_after; + int ret; + long page_size; + struct dma_heap_allocation_data *req; + + ksft_print_msg("Testing fd leak when copy_to_user() fails:\n"); + + heap_fd = dmabuf_heap_open(heap_name); + + page_size = sysconf(_SC_PAGESIZE); + + /* + * Place the ioctl argument in its own private anonymous page so + * we can flip its protection independently. + */ + req = mmap(NULL, page_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (req == MAP_FAILED) { + ksft_test_result_fail("mmap failed: %s\n", strerror(errno)); + goto out; + } + + memset(req, 0, sizeof(*req)); + req->len = page_size; + req->fd_flags = O_RDWR | O_CLOEXEC; + + fd_before = count_open_fds(); + if (fd_before < 0) { + ksft_test_result_fail("count_open_fds: %s\n", strerror(errno)); + munmap(req, page_size); + goto out; + } + + /* + * Make the page read-only so copy_to_user() will fault. The + * ioctl must fail with -1; if it returns success the test setup + * is broken (mprotect is synchronous, so there is no race). + */ + mprotect(req, page_size, PROT_READ); + + ret = ioctl(heap_fd, DMA_HEAP_IOCTL_ALLOC, req); + + /* Re-allow writes so munmap can clean up */ + mprotect(req, page_size, PROT_READ | PROT_WRITE); + munmap(req, page_size); + + if (ret != -1) { + ksft_test_result_fail("ioctl returned %d, expected -1 EFAULT\n", + ret); + goto out; + } + + fd_after = count_open_fds(); + if (fd_after < 0) { + ksft_test_result_fail("count_open_fds: %s\n", strerror(errno)); + goto out; + } + + ksft_test_result(fd_before == fd_after, + "fd leak on EFAULT: before=%d after=%d\n", + fd_before, fd_after); +out: + close(heap_fd); +} + static int numer_of_heaps(void) { DIR *d = opendir(DEVPATH); @@ -420,7 +530,7 @@ int main(void) return KSFT_SKIP; } - ksft_set_plan(11 * numer_of_heaps()); + ksft_set_plan(12 * numer_of_heaps()); while ((dir = readdir(d))) { if (!strncmp(dir->d_name, ".", 2)) @@ -435,6 +545,7 @@ int main(void) test_alloc_zeroed(dir->d_name, ONE_MEG); test_alloc_compat(dir->d_name); test_alloc_errors(dir->d_name); + test_alloc_no_fd_leak_on_efault(dir->d_name); } closedir(d); -- 2.34.1