From nobody Wed Feb 11 08:36:04 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C475543166; Wed, 29 Jan 2025 00:17:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738109874; cv=none; b=dZyGBqsguICjf5ZNLZb00t/5eVp19xx4OhqE/kSwUYjlQwRT5OdIZt5C5qu/e5e7j4fATk11R4K5i0KfLq1tyrl+j5P/2/nl5Fl4vzZFI5oB4XUI2KhtmxCqO/16NwbGZ2l+o5SoaTwhxQ9jOFYSBArl71BmMrsB/6bRWjbgmYU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738109874; c=relaxed/simple; bh=rhcPxDE/hGrU4tf9/2EyzDn71kVa3O0+HXsB6rQX/xg=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=aVnzb/G+R1Tq+yka/FC6aHwL6U/OWLeK8280Xwwrrfjkky4JL3j348TPiCFl09auNOIFF8e+XGz9ZQWhdKFK/G7v+wAcTdHpwHQOMGCQ8QLXXW0qV7rsL4wRFEGdUyj0gC/tVuCFkmfjcX5CyW1xu7UmcJcst8oWAnQuZrwbnls= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XMQr51eX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XMQr51eX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7FF80C4CED3; Wed, 29 Jan 2025 00:17:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738109874; bh=rhcPxDE/hGrU4tf9/2EyzDn71kVa3O0+HXsB6rQX/xg=; h=From:To:Cc:Subject:Date:From; b=XMQr51eXkbgeqEBNx86SM3BNnHtKhdZ+DwW0CQw3KFQaBJU4p+Xa/y4x+vBGlceeM J8T/UOk/6HEc6WyfirILBWGMo/CidLMIuS/xexztcRoWWEtQNmQUHwRfVNuGJ6c2mk ebLST4lm8SjTzlGN5/d4TE5OW1pnRPVn1+L1VCOelReXoCWC+tPyLieXsFo1soWERW rBy6NjICdHHW8f6yVqVzWn8fgdhOpd/1YZQbmzOEYoz7YgvuKb8GrCiqBLsb130PUe MJXcGsFpKLnYoOd6jUFngLM5O+hh5dVbLmGpqzVg68ot6KJamoPW9CRdVpFjkk7T1p JtL10Th6zOpwA== From: Andrii Nakryiko To: linux-mm@kvack.org, akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, brauner@kernel.org, viro@zeniv.linux.org.uk Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, peterz@infradead.org, mingo@kernel.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, shakeel.butt@linux.dev, rppt@kernel.org, liam.howlett@oracle.com, surenb@google.com, kees@kernel.org, jannh@google.com, Andrii Nakryiko Subject: [PATCH] docs,procfs: document /proc/PID/* access permission checks Date: Tue, 28 Jan 2025 16:17:47 -0800 Message-ID: <20250129001747.759990-1-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: linux-kernel@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" Add a paragraph explaining what sort of capabilities a process would need to read procfs data for some other process. Also mention that reading data for its own process doesn't require any extra permissions. Signed-off-by: Andrii Nakryiko Reviewed-by: Shakeel Butt --- Documentation/filesystems/proc.rst | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems= /proc.rst index 09f0aed5a08b..0e7825bb1e3a 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -128,6 +128,16 @@ process running on the system, which is named after th= e process ID (PID). The link 'self' points to the process reading the file system. Each pro= cess subdirectory has the entries listed in Table 1-1. =20 +A process can read its own information from /proc/PID/* with no extra +permissions. When reading /proc/PID/* information for other processes, rea= ding +process is required to have either CAP_SYS_PTRACE capability with +PTRACE_MODE_READ access permissions, or, alternatively, CAP_PERFMON +capability. This applies to all read-only information like `maps`, `enviro= n`, +`pagemap`, etc. The only exception is `mem` file due to its read-write nat= ure, +which requires CAP_SYS_PTRACE capabilities with more elevated +PTRACE_MODE_ATTACH permissions; CAP_PERFMON capability does not grant acce= ss +to /proc/PID/mem for other processes. + Note that an open file descriptor to /proc/ or to any of its contained files or subdirectories does not prevent being reused for some other process in the event that exits. Operations on --=20 2.43.5