Ryusuke Konishi ffe5ebdf81 nilfs2: fix null pointer dereference at nilfs_segctor_do_construct() ... commit 8301c719a2 upstream. After commit c3aab9a0bd ("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: c3aab9a0bd ("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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-06-17 16:40:29 +02:00
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Kconfig	…
Makefile	…
alloc.c	…
alloc.h	…
bmap.c	…
bmap.h	…
btnode.c	…
btnode.h	…
btree.c	…
btree.h	…
cpfile.c	…
cpfile.h	…
dat.c	…
dat.h	…
dir.c	…
direct.c	…
direct.h	…
export.h	…
file.c	…
gcinode.c	…
ifile.c	…
ifile.h	…
inode.c	…
ioctl.c	…
mdt.c	…
mdt.h	…
namei.c	…
nilfs.h	…
page.c	…
page.h	…
recovery.c	…
segbuf.c	…
segbuf.h	…
segment.c	nilfs2: fix null pointer dereference at nilfs_segctor_do_construct()	2020-06-17 16:40:29 +02:00
segment.h	…
sufile.c	…
sufile.h	…
super.c	…
sysfs.c	…
sysfs.h	…
the_nilfs.c	…
the_nilfs.h	…