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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, hdk1983@gmail.com,
	hermes@ceres.dti.ne.jp, konishi.ryusuke@gmail.com,
	linux-mm@kvack.org, me@waltonhoops.com,
	mm-commits@vger.kernel.org, stable@vger.kernel.org,
	tom@logand.com, torvalds@linux-foundation.org
Subject: [patch 05/25] nilfs2: fix null pointer dereference at nilfs_segctor_do_construct()
Date: Wed, 10 Jun 2020 18:41:35 -0700	[thread overview]
Message-ID: <20200611014135.qj6WrSl6h%akpm__46696.0384904937$1591839706$gmane$org@linux-foundation.org> (raw)
In-Reply-To: <20200610184053.3fa7368ab80e23bfd44de71f@linux-foundation.org>

From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Subject: nilfs2: fix null pointer dereference at nilfs_segctor_do_construct()

After commit c3aab9a0bd91 ("mm/filemap.c: don't initiate writeback if
mapping has no dirty pages"), the following null pointer dereference has
been reported on nilfs2:

 BUG: kernel NULL pointer dereference, address: 00000000000000a8
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: 0000 [#1] SMP PTI
 ...
 RIP: 0010:percpu_counter_add_batch+0xa/0x60
 ...
 Call Trace:
  __test_set_page_writeback+0x2d3/0x330
  nilfs_segctor_do_construct+0x10d3/0x2110 [nilfs2]
  nilfs_segctor_construct+0x168/0x260 [nilfs2]
  nilfs_segctor_thread+0x127/0x3b0 [nilfs2]
  kthread+0xf8/0x130
  ...

This crash turned out to be caused by set_page_writeback() call for
segment summary buffers at nilfs_segctor_prepare_write().

set_page_writeback() can call inc_wb_stat(inode_to_wb(inode),
WB_WRITEBACK) where inode_to_wb(inode) is NULL if the inode of
underlying block device does not have an associated wb.

This fixes the issue by calling inode_attach_wb() in advance to ensure
to associate the bdev inode with its wb.

Link: http://lkml.kernel.org/r/20200608.011819.1399059588922299158.konishi.ryusuke@gmail.com
Fixes: c3aab9a0bd91 ("mm/filemap.c: don't initiate writeback if mapping has no dirty pages")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: Walton Hoops <me@waltonhoops.com>
Reported-by: Tomas Hlavaty <tom@logand.com>
Reported-by: ARAI Shun-ichi <hermes@ceres.dti.ne.jp>
Reported-by: Hideki EIRAKU <hdk1983@gmail.com>
Cc: <stable@vger.kernel.org>	[5.4+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/nilfs2/segment.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/nilfs2/segment.c~nilfs2-fix-null-pointer-dereference-at-nilfs_segctor_do_construct
+++ a/fs/nilfs2/segment.c
@@ -2780,6 +2780,8 @@ int nilfs_attach_log_writer(struct super
 	if (!nilfs->ns_writer)
 		return -ENOMEM;
 
+	inode_attach_wb(nilfs->ns_bdev->bd_inode, NULL);
+
 	err = nilfs_segctor_start_thread(nilfs->ns_writer);
 	if (err) {
 		kfree(nilfs->ns_writer);
_

  parent reply	other threads:[~2020-06-11  1:41 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-11  1:40 incoming Andrew Morton
2020-06-11  1:41 ` [patch 01/25] khugepaged: selftests: fix timeout condition in wait_for_scan() Andrew Morton
2020-06-11  1:41 ` [patch 02/25] scripts/spelling: add a few more typos Andrew Morton
2020-06-11  1:41 ` [patch 03/25] kcov: check kcov_softirq in kcov_remote_stop() Andrew Morton
2020-06-11  1:41 ` [patch 04/25] lib/lz4/lz4_decompress.c: document deliberate use of `&' Andrew Morton
2020-06-11  1:41 ` Andrew Morton [this message]
2020-06-11  1:41 ` [patch 06/25] checkpatch: correct check for kernel parameters doc Andrew Morton
2020-06-11  1:41 ` [patch 07/25] lib: fix bitmap_parse() on 64-bit big endian archs Andrew Morton
2020-06-11  1:41 ` [patch 08/25] mm/debug_vm_pgtable: fix kernel crash by checking for THP support Andrew Morton
2020-06-11  1:41 ` [patch 09/25] ocfs2: fix spelling mistake and grammar Andrew Morton
2020-06-11  1:41 ` [patch 10/25] mm: add comments on pglist_data zones Andrew Morton
2020-06-11  1:41 ` [patch 11/25] lib: test get_count_order/long in test_bitops.c Andrew Morton
2020-06-11  1:41 ` [patch 12/25] stacktrace: cleanup inconsistent variable type Andrew Morton
2020-06-11  1:41 ` [patch 13/25] kernel: move use_mm/unuse_mm to kthread.c Andrew Morton
2020-06-11  1:42 ` [patch 14/25] " Andrew Morton
2020-06-11  1:42 ` [patch 15/25] kernel: better document the use_mm/unuse_mm API contract Andrew Morton
2020-06-11  1:42 ` [patch 16/25] kernel: set USER_DS in kthread_use_mm Andrew Morton
2020-06-11  1:42 ` [patch 17/25] mm/madvise: pass task and mm to do_madvise Andrew Morton
2020-06-11  1:42 ` [patch 18/25] mm/madvise: introduce process_madvise() syscall: an external memory hinting API Andrew Morton
2020-06-11  1:42 ` [patch 19/25] mm/madvise: check fatal signal pending of target process Andrew Morton
2020-06-11  1:42 ` [patch 20/25] pid: move pidfd_get_pid() to pid.c Andrew Morton
2020-06-11  1:42 ` [patch 21/25] mm/madvise: support both pid and pidfd for process_madvise Andrew Morton
2020-06-11  1:42 ` [patch 22/25] mm/madvise: allow KSM hints for remote API Andrew Morton
2020-06-11  1:42 ` [patch 23/25] mm: support vector address ranges for process_madvise Andrew Morton
2020-06-11  1:42 ` [patch 24/25] mm: use only pidfd for process_madvise syscall Andrew Morton
2020-06-11  1:42 ` [patch 25/25] mm/madvise.c: remove duplicated include Andrew Morton
2020-06-11  5:25 ` [to-be-updated] mm-pass-task-and-mm-to-do_madvise.patch removed from -mm tree Andrew Morton
2020-06-11  5:26 ` [to-be-updated] mm-introduce-external-memory-hinting-api.patch " Andrew Morton
2020-06-11  5:26 ` [to-be-updated] mm-check-fatal-signal-pending-of-target-process.patch " Andrew Morton
2020-06-11  5:26 ` [to-be-updated] pid-move-pidfd_get_pid-function-to-pidc.patch " Andrew Morton
2020-06-11  5:26 ` [to-be-updated] mm-support-both-pid-and-pidfd-for-process_madvise.patch " Andrew Morton
2020-06-11  5:26 ` [to-be-updated] mm-madvise-allow-ksm-hints-for-remote-api.patch " Andrew Morton
2020-06-11  5:26 ` [to-be-updated] mm-support-vector-address-ranges-for-process_madvise.patch " Andrew Morton
2020-06-11  5:26 ` [to-be-updated] mm-use-only-pidfd-for-process_madvise-syscall.patch " Andrew Morton

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