* Re: + seq_read-info-message-about-buggy-next-functions.patch added to -mm tree [not found] <20200226035621.4NlNn738T%akpm@linux-foundation.org> @ 2020-03-02 18:20 ` Qian Cai 2020-03-02 19:31 ` Qian Cai 0 siblings, 1 reply; 4+ messages in thread From: Qian Cai @ 2020-03-02 18:20 UTC (permalink / raw) To: linux-kernel, dave, longman, manfred, mingo, mm-commits, neilb, oberpar, rostedt, viro, vvs Cc: akpm On Tue, 2020-02-25 at 19:56 -0800, Andrew Morton wrote: > ------------------------------------------------------ > From: Vasily Averin <vvs@virtuozzo.com> > Subject: fs/seq_file.c: seq_read(): add info message about buggy .next functions > > Patch series "seq_file .next functions should increase position index". > > 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 > > > This patch (of 4): > > Add debug code to seq_read() to detect missed or out-of-tree incorrect > .next seq_file functions. This patch spams the console like crazy while reading sysfs, # dmesg | grep 'buggy seq_file' | wc -l 4204 [ 9505.321981] LTP: starting read_all_proc (read_all -d /proc -q -r 10) [ 9508.222934] buggy seq_file .next function xt_match_seq_next [x_tables] did not updated position index [ 9508.223319] buggy seq_file .next function xt_match_seq_next [x_tables] did not updated position index [ 9508.223654] buggy seq_file .next function xt_match_seq_next [x_tables] did not updated position index [ 9508.223994] buggy seq_file .next function xt_match_seq_next [x_tables] did not updated position index [ 9508.224337] buggy seq_file .next function xt_match_seq_next [x_tables] did not updated position index ... > > https://bugzilla.kernel.org/show_bug.cgi?id=206283 > Link: http://lkml.kernel.org/r/244674e5-760c-86bd-d08a-047042881748@virtuozzo.com > Link: http://lkml.kernel.org/r/7c24087c-e280-e580-5b0c-0cdaeb14cd18@virtuozzo.com > Signed-off-by: Vasily Averin <vvs@virtuozzo.com> > Cc: NeilBrown <neilb@suse.com> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Davidlohr Bueso <dave@stgolabs.net> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Manfred Spraul <manfred@colorfullife.com> > Cc: Peter Oberparleiter <oberpar@linux.ibm.com> > Cc: Waiman Long <longman@redhat.com> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > fs/seq_file.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > --- a/fs/seq_file.c~seq_read-info-message-about-buggy-next-functions > +++ a/fs/seq_file.c > @@ -256,9 +256,12 @@ Fill: > loff_t pos = m->index; > > p = m->op->next(m, p, &m->index); > - if (pos == m->index) > - /* Buggy ->next function */ > + if (pos == m->index) { > + pr_info("buggy seq_file .next function %ps " > + "did not updated position index\n", > + m->op->next); > m->index++; > + } > if (!p || IS_ERR(p)) { > err = PTR_ERR(p); > break; > _ > > Patches currently in -mm which might be from vvs@virtuozzo.com are > > seq_read-info-message-about-buggy-next-functions.patch > pstore_ftrace_seq_next-should-increase-position-index.patch > gcov_seq_next-should-increase-position-index.patch > sysvipc_find_ipc-should-increase-position-index.patch > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: + seq_read-info-message-about-buggy-next-functions.patch added to -mm tree 2020-03-02 18:20 ` + seq_read-info-message-about-buggy-next-functions.patch added to -mm tree Qian Cai @ 2020-03-02 19:31 ` Qian Cai 2020-03-02 20:42 ` Andrew Morton 0 siblings, 1 reply; 4+ messages in thread From: Qian Cai @ 2020-03-02 19:31 UTC (permalink / raw) To: linux-kernel, dave, longman, manfred, mingo, mm-commits, neilb, oberpar, rostedt, viro, vvs Cc: akpm On Mon, 2020-03-02 at 13:20 -0500, Qian Cai wrote: > This patch spams the console like crazy while reading sysfs, > > # dmesg | grep 'buggy seq_file' | wc -l > 4204 > > [ 9505.321981] LTP: starting read_all_proc (read_all -d /proc -q -r 10) > [ 9508.222934] buggy seq_file .next function xt_match_seq_next [x_tables] did > not updated position index > [ 9508.223319] buggy seq_file .next function xt_match_seq_next [x_tables] did > not updated position index > [ 9508.223654] buggy seq_file .next function xt_match_seq_next [x_tables] did > not updated position index > [ 9508.223994] buggy seq_file .next function xt_match_seq_next [x_tables] did > not updated position index > [ 9508.224337] buggy seq_file .next function xt_match_seq_next [x_tables] did > not updated position index > ... > > > > > > https://bugzilla.kernel.org/show_bug.cgi?id=206283 > > Link: http://lkml.kernel.org/r/244674e5-760c-86bd-d08a-047042881748@virtuozzo.com > > Link: http://lkml.kernel.org/r/7c24087c-e280-e580-5b0c-0cdaeb14cd18@virtuozzo.com > > Signed-off-by: Vasily Averin <vvs@virtuozzo.com> > > Cc: NeilBrown <neilb@suse.com> > > Cc: Al Viro <viro@zeniv.linux.org.uk> > > Cc: Steven Rostedt <rostedt@goodmis.org> > > Cc: Davidlohr Bueso <dave@stgolabs.net> > > Cc: Ingo Molnar <mingo@redhat.com> > > Cc: Manfred Spraul <manfred@colorfullife.com> > > Cc: Peter Oberparleiter <oberpar@linux.ibm.com> > > Cc: Waiman Long <longman@redhat.com> > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > > --- > > > > fs/seq_file.c | 7 +++++-- > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > > --- a/fs/seq_file.c~seq_read-info-message-about-buggy-next-functions > > +++ a/fs/seq_file.c > > @@ -256,9 +256,12 @@ Fill: > > loff_t pos = m->index; > > > > p = m->op->next(m, p, &m->index); > > - if (pos == m->index) > > - /* Buggy ->next function */ > > + if (pos == m->index) { > > + pr_info("buggy seq_file .next function %ps " > > + "did not updated position index\n", > > + m->op->next); This? s/pr_info/pr_info_ratelimited/ > > m->index++; > > + } > > if (!p || IS_ERR(p)) { > > err = PTR_ERR(p); > > break; > > _ > > > > Patches currently in -mm which might be from vvs@virtuozzo.com are > > > > seq_read-info-message-about-buggy-next-functions.patch > > pstore_ftrace_seq_next-should-increase-position-index.patch > > gcov_seq_next-should-increase-position-index.patch > > sysvipc_find_ipc-should-increase-position-index.patch > > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: + seq_read-info-message-about-buggy-next-functions.patch added to -mm tree 2020-03-02 19:31 ` Qian Cai @ 2020-03-02 20:42 ` Andrew Morton 2020-03-03 5:36 ` Vasily Averin 0 siblings, 1 reply; 4+ messages in thread From: Andrew Morton @ 2020-03-02 20:42 UTC (permalink / raw) To: Qian Cai Cc: linux-kernel, dave, longman, manfred, mingo, mm-commits, neilb, oberpar, rostedt, viro, vvs On Mon, 02 Mar 2020 14:31:48 -0500 Qian Cai <cai@lca.pw> wrote: > On Mon, 2020-03-02 at 13:20 -0500, Qian Cai wrote: > > This patch spams the console like crazy while reading sysfs, > > > > # dmesg | grep 'buggy seq_file' | wc -l > > 4204 > > > > [ 9505.321981] LTP: starting read_all_proc (read_all -d /proc -q -r 10) > > [ 9508.222934] buggy seq_file .next function xt_match_seq_next [x_tables] did > > not updated position index > > [ 9508.223319] buggy seq_file .next function xt_match_seq_next [x_tables] did > > not updated position index > > [ 9508.223654] buggy seq_file .next function xt_match_seq_next [x_tables] did > > not updated position index > > [ 9508.223994] buggy seq_file .next function xt_match_seq_next [x_tables] did > > not updated position index > > [ 9508.224337] buggy seq_file .next function xt_match_seq_next [x_tables] did > > not updated position index > > ... > > > > > > > --- a/fs/seq_file.c~seq_read-info-message-about-buggy-next-functions > > > +++ a/fs/seq_file.c > > > @@ -256,9 +256,12 @@ Fill: > > > loff_t pos = m->index; > > > > > > p = m->op->next(m, p, &m->index); > > > - if (pos == m->index) > > > - /* Buggy ->next function */ > > > + if (pos == m->index) { > > > + pr_info("buggy seq_file .next function %ps " > > > + "did not updated position index\n", > > > + m->op->next); > > This? > > s/pr_info/pr_info_ratelimited/ > Fair enough - I made that change. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: + seq_read-info-message-about-buggy-next-functions.patch added to -mm tree 2020-03-02 20:42 ` Andrew Morton @ 2020-03-03 5:36 ` Vasily Averin 0 siblings, 0 replies; 4+ messages in thread From: Vasily Averin @ 2020-03-03 5:36 UTC (permalink / raw) To: Andrew Morton, Qian Cai Cc: linux-kernel, dave, longman, manfred, mingo, mm-commits, neilb, oberpar, rostedt, viro, netfilter-devel, Pablo Neira Ayuso On 3/2/20 11:42 PM, Andrew Morton wrote: > On Mon, 02 Mar 2020 14:31:48 -0500 Qian Cai <cai@lca.pw> wrote: > >> On Mon, 2020-03-02 at 13:20 -0500, Qian Cai wrote: >>> This patch spams the console like crazy while reading sysfs, >>> >>> # dmesg | grep 'buggy seq_file' | wc -l >>> 4204 >>> >>> [ 9505.321981] LTP: starting read_all_proc (read_all -d /proc -q -r 10) >>> [ 9508.222934] buggy seq_file .next function xt_match_seq_next [x_tables] did >>> not updated position index >>> [ 9508.223319] buggy seq_file .next function xt_match_seq_next [x_tables] did >>> not updated position index >>> [ 9508.223654] buggy seq_file .next function xt_match_seq_next [x_tables] did >>> not updated position index >>> [ 9508.223994] buggy seq_file .next function xt_match_seq_next [x_tables] did >>> not updated position index >>> [ 9508.224337] buggy seq_file .next function xt_match_seq_next [x_tables] did >>> not updated position index It should be fixed by following patch-set submitted to Netfilter-Devel mailing list [PATCH v2 0/4] netfilter: seq_file .next functions should increase position index https://lore.kernel.org/netfilter-devel/497a82c1-7b6a-adf4-a4ce-df46fe436aae@virtuozzo.com/T/ >>>> --- a/fs/seq_file.c~seq_read-info-message-about-buggy-next-functions >>>> +++ a/fs/seq_file.c >>>> @@ -256,9 +256,12 @@ Fill: >>>> loff_t pos = m->index; >>>> >>>> p = m->op->next(m, p, &m->index); >>>> - if (pos == m->index) >>>> - /* Buggy ->next function */ >>>> + if (pos == m->index) { >>>> + pr_info("buggy seq_file .next function %ps " >>>> + "did not updated position index\n", >>>> + m->op->next); >> >> This? >> >> s/pr_info/pr_info_ratelimited/ >> > > Fair enough - I made that change. > ^ permalink raw reply [flat|nested] 4+ messages in thread
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[not found] <20200226035621.4NlNn738T%akpm@linux-foundation.org>
2020-03-02 18:20 ` + seq_read-info-message-about-buggy-next-functions.patch added to -mm tree Qian Cai
2020-03-02 19:31 ` Qian Cai
2020-03-02 20:42 ` Andrew Morton
2020-03-03 5:36 ` Vasily Averin
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