From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, dave@stgolabs.net, linux-mm@kvack.org,
longman@redhat.com, manfred@colorfullife.com, mingo@redhat.com,
mm-commits@vger.kernel.org, neilb@suse.com,
oberpar@linux.ibm.com, rostedt@goodmis.org,
torvalds@linux-foundation.org, viro@zeniv.linux.org.uk,
vvs@virtuozzo.com
Subject: [patch 33/35] fs/seq_file.c: seq_read(): add info message about buggy .next functions
Date: Fri, 10 Apr 2020 14:34:06 -0700 [thread overview]
Message-ID: <20200410213406.YKfS5tNA-%akpm@linux-foundation.org> (raw)
In-Reply-To: <20200410143047.bf34a933ce1affdc042c7c80@linux-foundation.org>
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.
[akpm@linux-foundation.org: s/pr_info/pr_info_ratelimited/, per Qian Cai]
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
@@ -232,9 +232,12 @@ 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_ratelimited("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;
_
next prev parent reply other threads:[~2020-04-10 21:34 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-10 21:30 incoming Andrew Morton
2020-04-10 21:32 ` [patch 01/35] hfsplus: fix crash and filesystem corruption when deleting files Andrew Morton
2020-04-10 21:32 ` [patch 02/35] mm, memcg: do not high throttle allocators based on wraparound Andrew Morton
2020-04-10 21:32 ` [patch 03/35] mm, slab_common: fix a typo in comment "eariler"->"earlier" Andrew Morton
2020-04-10 21:32 ` [patch 04/35] docs: mm: slab.h: fix a broken cross-reference Andrew Morton
2020-04-10 21:32 ` [patch 05/35] mm/page_alloc.c: fix kernel-doc warning Andrew Morton
2020-04-10 21:32 ` [patch 06/35] mm/page_alloc: make pcpu_drain_mutex and pcpu_drain static Andrew Morton
2020-04-10 21:32 ` [patch 07/35] mm/gup: fix null pointer dereference detected by coverity Andrew Morton
2020-04-10 22:24 ` Linus Torvalds
2020-04-10 23:53 ` Peter Xu
2020-04-11 0:19 ` Linus Torvalds
2020-04-14 4:04 ` Miles Chen
2020-04-10 21:32 ` [patch 08/35] ocfs2: no need try to truncate file beyond i_size Andrew Morton
2020-04-10 21:32 ` [patch 09/35] mm: cma: NUMA node interface Andrew Morton
2020-04-10 21:32 ` [patch 10/35] mm: hugetlb: optionally allocate gigantic hugepages using cma Andrew Morton
2020-04-10 21:32 ` [patch 11/35] mm/mmap.c: initialize align_offset explicitly for vm_unmapped_area Andrew Morton
2020-04-10 21:32 ` [patch 12/35] mm/memory.c: refactor insert_page to prepare for batched-lock insert Andrew Morton
2020-04-10 21:32 ` [patch 13/35] mm: bring sparc pte_index() semantics inline with other platforms Andrew Morton
2020-04-10 21:32 ` [patch 14/35] mm: define pte_index as macro for x86 Andrew Morton
2020-04-10 21:33 ` [patch 15/35] mm/memory.c: add vm_insert_pages() Andrew Morton
2020-04-10 21:33 ` [patch 16/35] mm/vma: define a default value for VM_DATA_DEFAULT_FLAGS Andrew Morton
2020-04-10 21:33 ` [patch 17/35] mm/vma: introduce VM_ACCESS_FLAGS Andrew Morton
2020-04-10 21:33 ` [patch 18/35] mm/special: create generic fallbacks for pte_special() and pte_mkspecial() Andrew Morton
2020-04-10 21:33 ` [patch 19/35] mm/memory_hotplug: drop the flags field from struct mhp_restrictions Andrew Morton
2020-04-10 21:33 ` [patch 20/35] mm/memory_hotplug: rename mhp_restrictions to mhp_params Andrew Morton
2020-04-10 21:33 ` [patch 21/35] x86/mm: thread pgprot_t through init_memory_mapping() Andrew Morton
2020-04-10 21:33 ` [patch 22/35] x86/mm: introduce __set_memory_prot() Andrew Morton
2020-04-10 21:33 ` [patch 23/35] powerpc/mm: thread pgprot_t through create_section_mapping() Andrew Morton
2020-04-10 21:33 ` [patch 24/35] mm/memory_hotplug: add pgprot_t to mhp_params Andrew Morton
2020-04-10 21:33 ` [patch 25/35] mm/memremap: set caching mode for PCI P2PDMA memory to WC Andrew Morton
2020-04-10 21:33 ` [patch 26/35] kmod: make request_module() return an error when autoloading is disabled Andrew Morton
2020-04-10 21:33 ` [patch 27/35] fs/filesystems.c: downgrade user-reachable WARN_ONCE() to pr_warn_once() Andrew Morton
2020-04-10 21:33 ` [patch 28/35] docs: admin-guide: document the kernel.modprobe sysctl Andrew Morton
2020-04-10 21:33 ` [patch 29/35] selftests: kmod: fix handling test numbers above 9 Andrew Morton
2020-04-10 21:33 ` [patch 30/35] selftests: kmod: test disabling module autoloading Andrew Morton
2020-04-10 21:34 ` [patch 31/35] change email address for Pali Rohár Andrew Morton
2020-04-10 21:44 ` Joe Perches
2020-04-10 21:34 ` [patch 32/35] drivers/dma/tegra20-apb-dma.c: fix platform_get_irq.cocci warnings Andrew Morton
2020-04-13 17:54 ` Jon Hunter
2020-04-10 21:34 ` Andrew Morton [this message]
2020-04-10 21:34 ` [patch 34/35] kernel/gcov/fs.c: gcov_seq_next() should increase position index Andrew Morton
2020-04-10 21:34 ` [patch 35/35] ipc/util.c: sysvipc_find_ipc() " Andrew Morton
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