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| author | Ryusuke Konishi <konishi.ryusuke@gmail.com> | 2020-06-10 18:41:35 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-10 19:14:17 -0700 |
| commit | 8301c719a2bd131436438e49130ee381d30933f5 (patch) | |
| tree | f9d6847b8703ada7c53f9aceadec4a3aa69fdb39 /fs/nilfs2 | |
| parent | e8ec04938c446e5f4dc53e0147f0f679995012ee (diff) | |
| download | lwn-8301c719a2bd131436438e49130ee381d30933f5.tar.gz lwn-8301c719a2bd131436438e49130ee381d30933f5.zip | |
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.
Fixes: c3aab9a0bd91 ("mm/filemap.c: don't initiate writeback if mapping has no dirty pages")
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>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org> [5.4+]
Link: http://lkml.kernel.org/r/20200608.011819.1399059588922299158.konishi.ryusuke@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/nilfs2')
| -rw-r--r-- | fs/nilfs2/segment.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c index 445eef41bfaf..91b58c897f92 100644 --- a/fs/nilfs2/segment.c +++ b/fs/nilfs2/segment.c @@ -2780,6 +2780,8 @@ int nilfs_attach_log_writer(struct super_block *sb, struct nilfs_root *root) 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); |