Linux-Security-Module Archive on lore.kernel.org
 help / color / Atom feed
From: David Howells <dhowells@redhat.com>
To: torvalds@linux-foundation.org
Cc: dhowells@redhat.com,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Casey Schaufler <casey@schaufler-ca.com>,
	Stephen Smalley <sds@tycho.nsa.gov>,
	nicolas.dichtel@6wind.com, raven@themaw.net,
	Christian Brauner <christian@brauner.io>,
	dhowells@redhat.com, keyrings@vger.kernel.org,
	linux-usb@vger.kernel.org, linux-block@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications [ver #2]
Date: Thu, 07 Nov 2019 13:36:33 +0000
Message-ID: <157313379331.29677.5209561321495531328.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <157313371694.29677.15388731274912671071.stgit@warthog.procyon.org.uk>

Allow a buffer to be marked such that read() must return the entire buffer
in one go or return ENOBUFS.  Multiple buffers can be amalgamated into a
single read, but a short read will occur if the next "whole" buffer won't
fit.

This is useful for watch queue notifications to make sure we don't split a
notification across multiple reads, especially given that we need to
fabricate an overrun record under some circumstances - and that isn't in
the buffers.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/pipe.c                        |    8 +++++++-
 include/linux/pipe_fs_i.h        |    1 +
 kernel/watch_queue.c             |    2 +-
 samples/watch_queue/watch_test.c |    2 +-
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/pipe.c b/fs/pipe.c
index 099bf4b657dd..588355c24ee0 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -298,8 +298,14 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
 			size_t written;
 			int error;
 
-			if (chars > total_len)
+			if (chars > total_len) {
+				if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
+					if (ret == 0)
+						ret = -ENOBUFS;
+					break;
+				}
 				chars = total_len;
+			}
 
 			error = pipe_buf_confirm(pipe, buf);
 			if (error) {
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 816bc0d3aecd..a19d60a06869 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -8,6 +8,7 @@
 #define PIPE_BUF_FLAG_ATOMIC	0x02	/* was atomically mapped */
 #define PIPE_BUF_FLAG_GIFT	0x04	/* page is a gift */
 #define PIPE_BUF_FLAG_PACKET	0x08	/* read() as a packet */
+#define PIPE_BUF_FLAG_WHOLE	0x10	/* read() must return entire buffer or error */
 
 /**
  *	struct pipe_buffer - a linux kernel pipe buffer
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index b73fbfe0d467..b1d30296e29b 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -115,7 +115,7 @@ static bool post_one_notification(struct watch_queue *wqueue,
 	buf->ops = &watch_queue_pipe_buf_ops;
 	buf->offset = offset;
 	buf->len = len;
-	buf->flags = 0;
+	buf->flags = PIPE_BUF_FLAG_WHOLE;
 	pipe->head = head + 1;
 
 	if (!test_and_clear_bit(note, wqueue->notes_bitmap)) {
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 8925593bdb9b..f6fb6e813551 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -63,7 +63,7 @@ static void saw_key_change(struct watch_notification *n, size_t len)
  */
 static void consumer(int fd)
 {
-	unsigned char buffer[4096], *p, *end;
+	unsigned char buffer[433], *p, *end;
 	union {
 		struct watch_notification n;
 		unsigned char buf1[128];


  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB " David Howells
2019-11-07 13:35 ` [RFC PATCH 01/14] uapi: General notification queue definitions " David Howells
2019-11-07 13:35 ` [RFC PATCH 02/14] security: Add hooks to rule on setting a watch " David Howells
2019-11-07 13:35 ` [RFC PATCH 03/14] security: Add a hook for the point of notification insertion " David Howells
2019-11-07 13:35 ` [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE " David Howells
2019-11-07 18:16   ` Andy Lutomirski
2019-11-07 18:48   ` David Howells
2019-11-08  5:06     ` Andy Lutomirski
2019-11-08  6:42     ` David Howells
2019-11-07 13:36 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells
2019-11-07 13:36 ` [RFC PATCH 06/14] keys: Add a notification facility " David Howells
2019-11-07 13:36 ` [RFC PATCH 07/14] Add sample notification program " David Howells
2019-11-07 13:36 ` David Howells [this message]
2019-11-07 18:15   ` [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications " Andy Lutomirski
2019-11-07 18:23   ` David Howells
2019-11-07 13:36 ` [RFC PATCH 09/14] pipe: Add notification lossage handling " David Howells
2019-11-07 13:36 ` [RFC PATCH 10/14] Add a general, global device notification watch list " David Howells
2019-11-07 13:37 ` [RFC PATCH 11/14] block: Add block layer notifications " David Howells
2019-11-07 13:37 ` [RFC PATCH 12/14] usb: Add USB subsystem " David Howells
2019-11-07 13:37 ` [RFC PATCH 13/14] selinux: Implement the watch_key security hook " David Howells
2019-11-07 13:37 ` [RFC PATCH 14/14] smack: Implement the watch_key and post_notification hooks " David Howells
2019-11-07 17:16 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=157313379331.29677.5209561321495531328.stgit@warthog.procyon.org.uk \
    --to=dhowells@redhat.com \
    --cc=casey@schaufler-ca.com \
    --cc=christian@brauner.io \
    --cc=gregkh@linuxfoundation.org \
    --cc=keyrings@vger.kernel.org \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=nicolas.dichtel@6wind.com \
    --cc=raven@themaw.net \
    --cc=sds@tycho.nsa.gov \
    --cc=torvalds@linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Security-Module Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-security-module/0 linux-security-module/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-security-module linux-security-module/ https://lore.kernel.org/linux-security-module \
		linux-security-module@vger.kernel.org
	public-inbox-index linux-security-module

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-security-module


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git