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 47F52302752; Mon, 3 Nov 2025 11:27:19 +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=1762169239; cv=none; b=eCr8EAUzQoAXm2g8Sfu0/O3G8FPkFhQ/z/u6DqlCylIa4GeFXs9Fi0mOMRjXhbFG9b4K0QeVQTZwZSTLKlwuWFvo5DxzaqRHy5p6n6vCeze+pzSIRfH8xoot0QhdHpoe9fh3rEZUD5hJutuunohDYPncjAiBd0aeWDGKdqaIeDw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762169239; c=relaxed/simple; bh=nM6vUvQd4AMD+xtcLBWx9Qk09b196BZxjzjS13mYIcc=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=PxuszvqR1lrKFnRBIv6+3D/pKD1Rz+OEmKI5oeMIWTrtVWTTHo5pEZ5esUqJT720AeepBMw772xU5i8+xnhSX01mg+DHXh7k+S095D+skTT5rkk96l7aJ8LWD0RU1ovwexfIuyZHXIien6rrZeOy1MhnO67Txv2ZUBgizahrl0E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=r2H84mnV; 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="r2H84mnV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D419C4CEFD; Mon, 3 Nov 2025 11:27:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762169238; bh=nM6vUvQd4AMD+xtcLBWx9Qk09b196BZxjzjS13mYIcc=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=r2H84mnVSjhuIGEO5aLRQorevyb8zjgiiHeJZlPPmhXri/0/4PMO+OYDGVDt50NKB t0kn67GHFwA3X/jWuiYZuKDHgD+g1gfQrcbGiNZwci38VGJ07IFFvQozVUJs/dGnV7 nJHrrn/pV9R7ErJ65CuBBGwYTj7bJhGRaUo4JKPKQLV43ib/wO415hgFNLv/frAmAs hfp+Ykng5R99V6EcXlMks/+KbMSfMZHWO27TPXbywi+fYqp/PsHhqqHGmjW4AHNNkt SLDK+VhWs+5h/66bqjmnvlcuVtCVf1CXZfdTPwJZG8V4GX4N4ddhJ5/LMW6Jutesb7 2Mmj5DXtPgLVw== From: Christian Brauner Date: Mon, 03 Nov 2025 12:26:52 +0100 Subject: [PATCH 04/16] backing-file: use credential guards for writes 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-v1-4-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=3033; i=brauner@kernel.org; h=from:subject:message-id; bh=nM6vUvQd4AMD+xtcLBWx9Qk09b196BZxjzjS13mYIcc=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWRyTGzfO2uy4qzbchqXxHO5jrbyGT776n08N2zn67qjv IH3X6d87ShlYRDjYpAVU2RxaDcJl1vOU7HZKFMDZg4rE8gQBi5OAZiIeDXD/3DflS25m8pkl4uc /rlhwwKZR8KTu1oVjt2fl6HIqaf5Zx7D/9TpR5O508w/XTv+5owO47I/vx/cZDwjZ374u2TULvF ni5kA 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 | 74 +++++++++++++++++++++++++++++-------------------------- 1 file changed, 39 insertions(+), 35 deletions(-) diff --git a/fs/backing-file.c b/fs/backing-file.c index 4cb7276e7ead..9bea737d5bef 100644 --- a/fs/backing-file.c +++ b/fs/backing-file.c @@ -210,11 +210,47 @@ ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter, } EXPORT_SYMBOL_GPL(backing_file_read_iter); +static int do_backing_file_write_iter(struct file *file, struct iov_iter *iter, + struct kiocb *iocb, int flags, + void (*end_write)(struct kiocb *, ssize_t)) +{ + struct backing_aio *aio; + int ret; + + if (is_sync_kiocb(iocb)) { + rwf_t rwf = iocb_to_rw_flags(flags); + + ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf); + if (end_write) + end_write(iocb, ret); + return ret; + } + + ret = backing_aio_init_wq(iocb); + if (ret) + return ret; + + aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); + if (!aio) + return -ENOMEM; + + aio->orig_iocb = iocb; + aio->end_write = end_write; + kiocb_clone(&aio->iocb, iocb, get_file(file)); + aio->iocb.ki_flags = flags; + aio->iocb.ki_complete = backing_aio_queue_completion; + refcount_set(&aio->ref, 2); + ret = vfs_iocb_iter_write(file, &aio->iocb, iter); + backing_aio_put(aio); + if (ret != -EIOCBQUEUED) + backing_aio_cleanup(aio, ret); + return ret; +} + ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter, struct kiocb *iocb, int flags, struct backing_file_ctx *ctx) { - const struct cred *old_cred; ssize_t ret; if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) @@ -237,40 +273,8 @@ ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter, */ flags &= ~IOCB_DIO_CALLER_COMP; - old_cred = override_creds(ctx->cred); - if (is_sync_kiocb(iocb)) { - rwf_t rwf = iocb_to_rw_flags(flags); - - ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf); - if (ctx->end_write) - ctx->end_write(iocb, ret); - } else { - struct backing_aio *aio; - - ret = backing_aio_init_wq(iocb); - if (ret) - goto out; - - ret = -ENOMEM; - aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); - if (!aio) - goto out; - - aio->orig_iocb = iocb; - aio->end_write = ctx->end_write; - kiocb_clone(&aio->iocb, iocb, get_file(file)); - aio->iocb.ki_flags = flags; - aio->iocb.ki_complete = backing_aio_queue_completion; - refcount_set(&aio->ref, 2); - ret = vfs_iocb_iter_write(file, &aio->iocb, iter); - backing_aio_put(aio); - if (ret != -EIOCBQUEUED) - backing_aio_cleanup(aio, ret); - } -out: - revert_creds(old_cred); - - return ret; + with_creds(ctx->cred); + return do_backing_file_write_iter(file, iter, iocb, flags, ctx->end_write); } EXPORT_SYMBOL_GPL(backing_file_write_iter); -- 2.47.3