From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f172.google.com (mail-dy1-f172.google.com [74.125.82.172]) (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 5FC4633985 for ; Thu, 5 Mar 2026 00:52:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772671938; cv=none; b=Umz5jJUBulNxze56uMwDvLpxsZ3lemr5VMVh0HCjOJP4BiuiEjiQ54/3bMiG9RCVUqC1idANLDGU7eLXBbxy2YQEFVV5M3IJdNWaYwwDFD25TZaoBTiVK2fFy64A9GDRPCcea9dbZUY10THo/JnbEazEEnuoOc/tl80Mh3rDOqw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772671938; c=relaxed/simple; bh=z2kpQN8eXVzVRk+YNpEqT0u4alBsZfpx17Ir5hqpqwA=; h=Message-Id:In-Reply-To:References:From:Date:Subject:Content-Type: MIME-Version:To:Cc; b=Zi6Zv1qUjnSfP3DWPX5nJwYjfJQf8Q4yy3cE6Sj0kfu22YiM7agccs4DIvFwmAIBWKuXwGV+Y8RnEBtPlP6twB5VMk+Avtu7rgWw8F9LKlN2zw9vwq8y2wNqdxgCJ/rbd2Yy9Hkl/kKyYjXJEuf32qQWonlY5ciS59mrVPWji3M= 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=VNvh9uK3; arc=none smtp.client-ip=74.125.82.172 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="VNvh9uK3" Received: by mail-dy1-f172.google.com with SMTP id 5a478bee46e88-2bdd40d3c61so6188819eec.1 for ; Wed, 04 Mar 2026 16:52:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1772671935; x=1773276735; darn=vger.kernel.org; h=cc:to:mime-version:content-transfer-encoding:fcc:subject:date:from :references:in-reply-to:message-id:from:to:cc:subject:date :message-id:reply-to; bh=FVCxtZ9T9BCseA1BVQktZq/fH62L/SMOtAfjZOemys8=; b=VNvh9uK3WrHx81hr7VReftOTzJsyR1NdXWxdbttjrLr9Ctd5KYBtrEfQVyM9oREhOv ivlz0dAHjkYjAgkKmNaJjUrSgrXDQ3vE39ZR+gLh6r7e0K5XPx5E61HC5y4SvNNr+SUC 50XvgnkOgTGCruU3b41uGuUC7A2otslAbxf90dU4tNrMSk9DOx5a/Dno57jOjiBe/k3D ipXjkvooHkJinTpsBds/ChZSHf/dMJGlHQ3sKOIM2mVg3XgiQcl50bq4845iBZv9ielx GqhOYFzVFB54hNQCJJ5SETlnMadJrsgEMojVWvqNGM3TsXn0VZcGghRWBvZEXdQInac5 3XJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1772671935; x=1773276735; h=cc:to:mime-version:content-transfer-encoding:fcc:subject:date:from :references:in-reply-to:message-id:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=FVCxtZ9T9BCseA1BVQktZq/fH62L/SMOtAfjZOemys8=; b=gKuitYX3qfSzAaOsqXLQNNzugWv7HK/YIK1HX4qDczN3l2IBe2tk4TzfHmdMWuHKH3 bKonn+wS7ivGnDW0KK+rvRe9CJCHWIwtd9hSMkFAdlxCdWF5HWsclM96quAEvnLSOUzy Q8pB4AHeFhuI2orr4mT5/8mLaB3SknX23DiqmV6mqjH5bZr+fLP9d+4B1GHFaLO58zQu yqOkRsM+GSEQtrHrTAbWcW/Uj1RP2jsPiFBjSbkU5ZIEcJwCsqe+1E+LXPim1GxGM7fs INX1N5Pxss2Ia06IWWgPDDMz1eqLb7l0G390Rk3INWAepgvu8Jj2NTsPiIbzGM4TC140 6u5w== X-Gm-Message-State: AOJu0Yym0qRFfBl0U/9d4FXGCGCs7RKUk517OBrUrIkydxVA29prhACF dO/B04BR45ZWaczY8tpH1ALQV6fXKwpJWRt6mOd15zbiLYyKqxELcgoq5FIDSA== X-Gm-Gg: ATEYQzxSt1z19tEJg2JSIRawIHLjzFhqjzws7qSqj7wr2doCgt6kuF6UnUqT35yJdnW VMeyGBxUKhQYjzY7FGdjtfX93WaiJTAnRChSypP7bIjTg/XfWBQ2V+NTvYX2AJIEGZpxwYpgVcU yfFJQAnOjnMlXphC0cN7u4bVPZcxBKQgmTIyvXAevZ2AMGMDSl2NyrTHnQ9smK4QnEoeLIALW0W 8+8mn2A33mWONLBMD6TGMS1+B7LUij1bRxdE3nREDleyjo3RUITRdhVsTQ6J4Xa3IBne5yA7CGM s/k66fQLtSDRtug56F+GpOxSae2SH2VNzsedojeKEUim4uxrBJPrXVe7Eq/OLx/VkaFOk5G79R7 4rgdNqPQ48KgHUHO5cVYlWvuSGuUrlDseZYOcMk5XyvU8jwTDht99o0YnF/qKHgQE22h6iCw5z8 Z6Y2CV1wfsmHDFAnshZeBguWUv X-Received: by 2002:a05:7300:dc8c:b0:2be:1803:7e11 with SMTP id 5a478bee46e88-2be311bd422mr1459826eec.30.1772671935043; Wed, 04 Mar 2026 16:52:15 -0800 (PST) Received: from [127.0.0.1] ([68.220.62.148]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2bdf662eb6dsm11575336eec.2.2026.03.04.16.52.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Mar 2026 16:52:14 -0800 (PST) Message-Id: <31fa1fb324be240e28bd360ee3afc45d8fb8444f.1772671920.git.gitgitgadget@gmail.com> In-Reply-To: References: From: "Paul Tarjan via GitGitGadget" Date: Thu, 05 Mar 2026 00:51:56 +0000 Subject: [PATCH v9 08/12] run-command: add pre-exec callback for child processes Fcc: Sent Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 To: git@vger.kernel.org Cc: Patrick Steinhardt , Paul Tarjan , Paul Tarjan , Paul Tarjan From: Paul Tarjan Add a pre_exec_cb function pointer to struct child_process that is invoked in the child between fork and exec. This gives callers a place to perform setup that must happen in the child's context, such as closing inherited file descriptors. Provide close_fd_above_stderr() as a ready-made callback that closes file descriptors 3 and above (skipping the child-notifier pipe), capped at sysconf(_SC_OPEN_MAX) or 4096, whichever is smaller. Signed-off-by: Paul Tarjan --- run-command.c | 15 +++++++++++++++ run-command.h | 15 +++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/run-command.c b/run-command.c index e3e02475cc..b9bc84ca1b 100644 --- a/run-command.c +++ b/run-command.c @@ -674,6 +674,18 @@ static void trace_run_command(const struct child_process *cp) strbuf_release(&buf); } +void close_fd_above_stderr(void) +{ + long max_fd = sysconf(_SC_OPEN_MAX); + int fd; + if (max_fd < 0 || max_fd > 4096) + max_fd = 4096; + for (fd = 3; fd < max_fd; fd++) { + if (fd != child_notifier) + close(fd); + } +} + int start_command(struct child_process *cmd) { int need_in, need_out, need_err; @@ -832,6 +844,9 @@ fail_pipe: child_close(cmd->out); } + if (cmd->pre_exec_cb) + cmd->pre_exec_cb(); + if (cmd->dir && chdir(cmd->dir)) child_die(CHILD_ERR_CHDIR); diff --git a/run-command.h b/run-command.h index 0df25e445f..7ea5c6e005 100644 --- a/run-command.h +++ b/run-command.h @@ -141,6 +141,14 @@ struct child_process { unsigned stdout_to_stderr:1; unsigned clean_on_exit:1; unsigned wait_after_clean:1; + + /** + * If set, the callback is invoked in the child between fork and + * exec. It can be used, for example, to close inherited file + * descriptors that the child should not keep open. + */ + void (*pre_exec_cb)(void); + void (*clean_on_exit_handler)(struct child_process *process); }; @@ -149,6 +157,13 @@ struct child_process { .env = STRVEC_INIT, \ } +/** + * Close file descriptors 3 and above. Suitable for use as a + * pre_exec_cb to prevent the child from inheriting pipe endpoints + * or other descriptors from the parent environment. + */ +void close_fd_above_stderr(void); + /** * The functions: start_command, finish_command, run_command do the following: * -- gitgitgadget