From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f46.google.com (mail-wr1-f46.google.com [209.85.221.46]) (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 633C140962A for ; Wed, 3 Jun 2026 09:44:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780479876; cv=none; b=swRl3xlTbhTSE69VkgjJo595n+bTAPLJ4A6OL8vJurSfqU4rTFGWltDhL3IMJI1m4sVFk8+WCtEPFpCwgzwGDd3P7FU6FaVEtuPEljwC5HnFT+x75j8A0mTAq7INQ8hj3vpnJBcoXjkHJjkStgx2gEksqg2Uo1wWq3THr8Ypodg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780479876; c=relaxed/simple; bh=RoX7XxjYXSu8G3YA+ItXU+wszRHFeBknMMYIYjavia0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=VQNYF80itEJ9StGmGvDOXI7kMNK+wkpq4vufZO2JG8ZR4WvopQM5swfStvcslOvmwoeSW0JI92TU3o7UaOMXs0SDEVq4MP8jCaeCZLpV2uI4uLLglk5unjpyki5fGZOjemCy/rFVVTOgMA2Zh75btDVyT0IDMJ8FJWQuTPd8foE= 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=WYArfYpr; arc=none smtp.client-ip=209.85.221.46 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="WYArfYpr" Received: by mail-wr1-f46.google.com with SMTP id ffacd0b85a97d-45efb698ef2so2220761f8f.3 for ; Wed, 03 Jun 2026 02:44:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1780479870; x=1781084670; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=HQvliPaluVt3hG4Df3aSiGvi4Xl7NzgZIMVV3aYBAsk=; b=WYArfYprWm1MPCkYA6GpO96UR6LtcCMbWN5mkVpuHKSXfkI9gI8Zx5NtGPwjaCcYyl DbzHGyr2S1MBGSdTjziE6+387tA0Aw8R5ylPwaJxZ8SjJqK4HlczdInIgSIkCiCrcMks gvcPEugBP6EQO2uCLib6YQCjEPhN4e+ad8erd56E/yTfLrIOxCTEsY9D+zJ2xANmIzQf N3y+2ivO+OyTGz4Ur0lKUUZaLrbNLNF3BZJ/nnz/PN4Tur39Hz5y5exZUiGpaBU/KX6p 4AnNNJDb6WFhbkyPEjeQt7bEFV9Q/+qAyZ9GbRwpiDy1SyBBv2fvNFIXCLMepW8DVDNT t2AA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780479870; x=1781084670; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=HQvliPaluVt3hG4Df3aSiGvi4Xl7NzgZIMVV3aYBAsk=; b=QHNMScvAkJLifo+TSwjMLkwxL8FGkMbqXKKInEas4vBDqfZbuKsFHc31Qf/yG3/dDY kNFvn1uv+TUyimRTAK20Gp++e3C9F856E7k80HRW9iuOqw8/RymNb7AjnexAOfIUTjZs pJFfC/nIH/vv0O8NwzX/WvZCsLMVNA131JpZvW+sA7FxytNqVLfoBdueBy9AJYN2AIf8 tnOaxGpIe2SsSNFWh228CxfOBrGt4evazAvXE9+EqYemX5h75xtLH23YSW8rODgNLy7P gUBagIKulMyTZQduFESgaGIi4uL9cVAwlrAywcGY/UbU4e0P/Ss/Xcq9zsUe8bMH6kDS Nhzw== X-Gm-Message-State: AOJu0Yz0xSgxqnhu+JYu0+rONL1ilVYAx4tHPLNW8klwTALInxFLtlmj IPnN1FS6RlsoquRBhqmBLU/V1KC7sGsydnGEPz8FG+lSPS70nicZ2PXfAL85n7VaoakPzw== X-Gm-Gg: Acq92OFre37KID/Nox/uJaPUp0GnbhTm9uAMVD11gW6znVjogvAByasSR6RDH+jww9U pcXQ9XYMS3zW+yoOy25yBSqX90TSECMiq7oi4y/Rrh356zyw+5nHkr5gCGjGGre583GaAPrV6aC m/UIGvRUQkyFdz7iwZ1/2UXnnssqrHerYJoREY2xEas5VSQEqE6piAJxe25nEHUOP7j9wkjwuU4 hxGacBfF83LuP1/t9zupQqQGOMOrTeH5Bc8TyiQRawH+uTTfPD0zUvSXXARmxg7RtJl1JnODejT Sjwt8LNBzgoXYyZr9xHh9QwYVYHYvCe2VWtiV9hUhr+z73V1Pue3jCxSIpL01abUJc2nkkf9lnq HuojmSCX51a3gTvWjCuCN5d85I3jPZQTbnmuN0QhiZ8z9Ulody27ZHonDTeZuT0eB7RF2KoqhAx DH/uoLZ5vGTzu0DAkAFWs9cMCASmGFBOlEOfl1ycCK2g== X-Received: by 2002:a05:6000:180c:b0:452:c9f:4b91 with SMTP id ffacd0b85a97d-46021781e28mr2648257f8f.4.1780479870353; Wed, 03 Jun 2026 02:44:30 -0700 (PDT) Received: from x1.tail0e71db.ts.net ([46.140.7.198]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4601f351ac0sm9989650f8f.27.2026.06.03.02.44.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jun 2026 02:44:30 -0700 (PDT) From: Ruslan Valiyev To: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, martin.lau@linux.dev, memxor@gmail.com Cc: song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org Subject: [PATCH bpf-next] selftests/bpf: add test for arena vma split and fork rejection Date: Wed, 3 Jun 2026 11:44:28 +0200 Message-ID: <20260603094428.2597058-1-linuxoid@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Verify that an arena map's mmap()ed VMA cannot be split with a partial munmap() or inherited across fork(). Before commit 4fddde2a732d ("bpf: Fix use-after-free in arena_vm_close on fork") the arena VMA had no .may_split callback and was not marked VM_DONTCOPY, so a splitting munmap() and a fork() both succeeded. The fork() case left the child with a VMA whose vml->vma still pointed at the parent, dangling after the parent unmapped and leading to a use-after-free if the child freed arena pages. The test creates an arena map, mmap()s it, and asserts that a splitting munmap() fails with -EINVAL and that the child of a fork() does not inherit the arena VMA. Signed-off-by: Ruslan Valiyev --- .../selftests/bpf/prog_tests/arena_fork.c | 58 +++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/arena_fork.c diff --git a/tools/testing/selftests/bpf/prog_tests/arena_fork.c b/tools/testing/selftests/bpf/prog_tests/arena_fork.c new file mode 100644 index 0000000000000..f3d5218c9e071 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/arena_fork.c @@ -0,0 +1,58 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include + +/* Regression test for commit 4fddde2a732d ("bpf: Fix use-after-free in + * arena_vm_close on fork"): an arena VMA must reject a splitting munmap() + * (.may_split) and must not be inherited across fork() (VM_DONTCOPY). On + * an unfixed kernel both operations succeed. + */ + +#define NR_PAGES 3 + +void test_arena_fork(void) +{ + LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE); + long ps = sysconf(_SC_PAGESIZE); + size_t sz = (size_t)NR_PAGES * ps; + int fd, ret, status, err; + void *area; + pid_t pid; + + fd = bpf_map_create(BPF_MAP_TYPE_ARENA, "arena_fork", 0, 0, NR_PAGES, &opts); + if (!ASSERT_OK_FD(fd, "arena map create")) + return; + + area = mmap(NULL, sz, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + if (!ASSERT_NEQ(area, MAP_FAILED, "mmap arena")) + goto close_fd; + + /* A split of the arena VMA must be rejected (.may_split). */ + ret = munmap((char *)area + ps, ps); + err = errno; + ASSERT_ERR(ret, "split munmap rejected"); + ASSERT_EQ(err, EINVAL, "split munmap errno"); + + /* The child of a fork() must not inherit the arena VMA (VM_DONTCOPY); + * mincore() returns ENOMEM for the unmapped range. + */ + pid = fork(); + if (ASSERT_GE(pid, 0, "fork")) { + if (pid == 0) { + unsigned char vec; + + _exit(mincore(area, ps, &vec) < 0 && errno == ENOMEM ? 0 : 1); + } + while ((ret = waitpid(pid, &status, 0)) < 0 && errno == EINTR) + ; + if (ASSERT_EQ(ret, pid, "waitpid")) + ASSERT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0, + "child must not inherit arena vma"); + } + + munmap(area, sz); +close_fd: + close(fd); +} base-commit: 174914ea551314c52a61713b9c4bde9e42d48073 -- 2.43.0