LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Vasily Averin <vvs@virtuozzo.com>
To: linux-kernel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	NeilBrown <neilb@suse.com>, Waiman Long <longman@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>
Subject: [PATCH 0/7] seq_file .next functions should increase position index
Date: Fri, 24 Jan 2020 10:02:36 +0300
Message-ID: <244674e5-760c-86bd-d08a-047042881748@virtuozzo.com> (raw)

In Aug 2018 NeilBrown noticed 
commit 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface")
"Some ->next functions do not increment *pos when they return NULL...
Note that such ->next functions are buggy and should be fixed. 
A simple demonstration is
   
dd if=/proc/swaps bs=1000 skip=1
    
Choose any block size larger than the size of /proc/swaps.  This will
always show the whole last line of /proc/swaps"

Described problem is still actual. If you make lseek into middle of last output line 
following read will output end of last line and whole last line once again.

$ dd if=/proc/swaps bs=1  # usual output
Filename				Type		Size	Used	Priority
/dev/dm-0                               partition	4194812	97536	-2
104+0 records in
104+0 records out
104 bytes copied

$ dd if=/proc/swaps bs=40 skip=1    # last line was generated twice
dd: /proc/swaps: cannot skip to specified offset
v/dm-0                               partition	4194812	97536	-2
/dev/dm-0                               partition	4194812	97536	-2 
3+1 records in
3+1 records out
131 bytes copied

There are lot of other affected files, I've found 30+ including
/proc/net/ip_tables_matches and /proc/sysvipc/*

I've sent patches into maillists of affected subsystems already,
this patch-set fixes the problem in files related to 
pstore, tracing, gcov, sysvipc  and other subsystems processed 
via linux-kernel@ mailing list directly

https://bugzilla.kernel.org/show_bug.cgi?id=206283

Vasily Averin (7):
  pstore_ftrace_seq_next should increase position index
  gcov_seq_next should increase position index
  t_next should increase position index
  fpid_next should increase position index
  eval_map_next should increase position index
  trigger_next should increase position index
  sysvipc_find_ipc should increase position index

 fs/pstore/inode.c                   | 2 +-
 ipc/util.c                          | 2 +-
 kernel/gcov/fs.c                    | 2 +-
 kernel/trace/ftrace.c               | 9 ++++++---
 kernel/trace/trace.c                | 4 +---
 kernel/trace/trace_events_trigger.c | 5 +++--
 6 files changed, 13 insertions(+), 11 deletions(-)

-- 
1.8.3.1


             reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-24  7:02 Vasily Averin [this message]
2020-01-24  7:47 ` [PATCH] seq_read: info message about buggy .next functions Vasily Averin
2020-01-24 15:50 ` [PATCH 0/7] seq_file .next functions should increase position index Steven Rostedt
2020-01-25  8:27   ` Vasily Averin

Reply instructions:

You may reply publicly 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=244674e5-760c-86bd-d08a-047042881748@virtuozzo.com \
    --to=vvs@virtuozzo.com \
    --cc=akpm@linux-foundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=longman@redhat.com \
    --cc=mingo@redhat.com \
    --cc=neilb@suse.com \
    --cc=oberpar@linux.ibm.com \
    --cc=rostedt@goodmis.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

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

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

Example config snippet for mirrors

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


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