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
next 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