From mboxrd@z Thu Jan 1 00:00:00 1970 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 6D5B53054DB; Mon, 3 Nov 2025 11:27:16 +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=1762169236; cv=none; b=dwS7E1NIpD8FQwmoIRjU23z12LVEDxx5yQXl67Z4lCRymRhA09AH0k6KWrR5easbwIAMDVYrjea/C3ZoCWaGwH7iNiC/9ioYNNFg7puV2ewTtiImXMD9PTFDtzYwkxoSPy3FjGFEhF9g7jGvhYtAohmxsh5mUS+hEf1fuMIUrs4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762169236; c=relaxed/simple; bh=Te6t6WBv6LcIE3Mz3jIDSKVou5veHZxj8ddg+uVgoIk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ovZKQQ2kCXvnk69xPwjn5oZpfmRaEKbYkSzmCIavlo9YWY59FnNQkgWqzIrbsOFRlhHBeFzFcV2vbYT0YDNGiQyt8I1a0rpOce4urOq0CLSm8bHIAb5S3YHkk/7wtuHa7t7flAVwquDGR9mI7BaxRm+ujLh/fCgXQvEKclAyEo8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sGzomzn+; 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="sGzomzn+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7ED62C116B1; Mon, 3 Nov 2025 11:27:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762169236; bh=Te6t6WBv6LcIE3Mz3jIDSKVou5veHZxj8ddg+uVgoIk=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=sGzomzn+PGDjvCwVJp7q7eb+dM1qxws72K6VH6xrXYmiGMTqrkYKH5g+ub4EUHZjN jAnATZTZMkKxvekdh/YRrdgGycnz6CGT3CDuRJR2YY0e1Zr4UyVqpldjAjR+bNT1u7 iiMA1FmOiSALrUAa+gellLW9ZhHuuud6bFbDlSAT77tgEqHbbjHusLuF2KHjkqvsvX VOetbNFCU0wnAJPhI53xqUam9lcXUp1hwNSpnKscop8OqOs6+t0/RoZDPoC30RwPkB OFF9MtFrUp0bTHvXUuLg9O5p9VvocMC31CLCjvY2a7BtHOKWiZL8k6PtoNchqYTvOd S3jdiMZckWqtw== From: Christian Brauner Date: Mon, 03 Nov 2025 12:26:51 +0100 Subject: [PATCH 03/16] backing-file: use credential guards for reads Precedence: bulk X-Mailing-List: linux-unionfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251103-work-creds-guards-simple-v1-3-a3e156839e7f@kernel.org> References: <20251103-work-creds-guards-simple-v1-0-a3e156839e7f@kernel.org> In-Reply-To: <20251103-work-creds-guards-simple-v1-0-a3e156839e7f@kernel.org> To: Linus Torvalds Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-aio@kvack.org, linux-unionfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, cgroups@vger.kernel.org, netdev@vger.kernel.org, Christian Brauner X-Mailer: b4 0.15-dev-96507 X-Developer-Signature: v=1; a=openpgp-sha256; l=2556; i=brauner@kernel.org; h=from:subject:message-id; bh=Te6t6WBv6LcIE3Mz3jIDSKVou5veHZxj8ddg+uVgoIk=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWRyTGz38X4ce1HzVa/FXFUmtYYbMyeKTlf3c6gz+HNeT UZ2t6dqRykLgxgXg6yYIotDu0m43HKeis1GmRowc1iZQIYwcHEKwETmNzIyrAgrqVBzevihy0q+ cEaCUKh4gH265rKLiUmZ3/MdWiJFGX4xPcraW37lS0tS87Zpued+eQrIv7x3fl4Qi0yXyfXruRy cAA== X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Use credential guards for scoped credential override with automatic restoration on scope exit. Signed-off-by: Christian Brauner --- fs/backing-file.c | 52 ++++++++++++++++++++++++++++------------------------ 1 file changed, 28 insertions(+), 24 deletions(-) diff --git a/fs/backing-file.c b/fs/backing-file.c index 15a7f8031084..4cb7276e7ead 100644 --- a/fs/backing-file.c +++ b/fs/backing-file.c @@ -157,13 +157,37 @@ static int backing_aio_init_wq(struct kiocb *iocb) return sb_init_dio_done_wq(sb); } +static int do_backing_file_read_iter(struct file *file, struct iov_iter *iter, + struct kiocb *iocb, int flags) +{ + struct backing_aio *aio = NULL; + int ret; + + if (is_sync_kiocb(iocb)) { + rwf_t rwf = iocb_to_rw_flags(flags); + + return vfs_iter_read(file, iter, &iocb->ki_pos, rwf); + } + + aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); + if (!aio) + return -ENOMEM; + + aio->orig_iocb = iocb; + kiocb_clone(&aio->iocb, iocb, get_file(file)); + aio->iocb.ki_complete = backing_aio_rw_complete; + refcount_set(&aio->ref, 2); + ret = vfs_iocb_iter_read(file, &aio->iocb, iter); + backing_aio_put(aio); + if (ret != -EIOCBQUEUED) + backing_aio_cleanup(aio, ret); + return ret; +} ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter, struct kiocb *iocb, int flags, struct backing_file_ctx *ctx) { - struct backing_aio *aio = NULL; - const struct cred *old_cred; ssize_t ret; if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) @@ -176,28 +200,8 @@ ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter, !(file->f_mode & FMODE_CAN_ODIRECT)) return -EINVAL; - old_cred = override_creds(ctx->cred); - if (is_sync_kiocb(iocb)) { - rwf_t rwf = iocb_to_rw_flags(flags); - - ret = vfs_iter_read(file, iter, &iocb->ki_pos, rwf); - } else { - ret = -ENOMEM; - aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); - if (!aio) - goto out; - - aio->orig_iocb = iocb; - kiocb_clone(&aio->iocb, iocb, get_file(file)); - aio->iocb.ki_complete = backing_aio_rw_complete; - refcount_set(&aio->ref, 2); - ret = vfs_iocb_iter_read(file, &aio->iocb, iter); - backing_aio_put(aio); - if (ret != -EIOCBQUEUED) - backing_aio_cleanup(aio, ret); - } -out: - revert_creds(old_cred); + scoped_with_creds(ctx->cred) + do_backing_file_read_iter(file, iter, iocb, flags); if (ctx->accessed) ctx->accessed(iocb->ki_filp); -- 2.47.3