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Subject[PATCH 5.2 088/137] f2fs: fix to drop meta/node pages during umount
Date
From: Chao Yu <yuchao0@huawei.com>

[ Upstream commit a8933b6b68f775b5774e7b075447fae13f4d01fe ]

As reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=204193

A null pointer dereference bug is triggered in f2fs under kernel-5.1.3.

kasan_report.cold+0x5/0x32
f2fs_write_end_io+0x215/0x650
bio_endio+0x26e/0x320
blk_update_request+0x209/0x5d0
blk_mq_end_request+0x2e/0x230
lo_complete_rq+0x12c/0x190
blk_done_softirq+0x14a/0x1a0
__do_softirq+0x119/0x3e5
irq_exit+0x94/0xe0
call_function_single_interrupt+0xf/0x20

During umount, we will access NULL sbi->node_inode pointer in
f2fs_write_end_io():

f2fs_bug_on(sbi, page->mapping == NODE_MAPPING(sbi) &&
page->index != nid_of_node(page));

The reason is if disable_checkpoint mount option is on, meta dirty
pages can remain during umount, and then be flushed by iput() of
meta_inode, however node_inode has been iput()ed before
meta_inode's iput().

Since checkpoint is disabled, all meta/node datas are useless and
should be dropped in next mount, so in umount, let's adjust
drop_inode() to give a hint to iput_final() to drop all those dirty
datas correctly.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/super.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 973f1e8187706..01038aff5d8e0 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -894,7 +894,21 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)

static int f2fs_drop_inode(struct inode *inode)
{
+ struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
int ret;
+
+ /*
+ * during filesystem shutdown, if checkpoint is disabled,
+ * drop useless meta/node dirty pages.
+ */
+ if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
+ if (inode->i_ino == F2FS_NODE_INO(sbi) ||
+ inode->i_ino == F2FS_META_INO(sbi)) {
+ trace_f2fs_drop_inode(inode, 1);
+ return 1;
+ }
+ }
+
/*
* This is to avoid a deadlock condition like below.
* writeback_single_inode(inode)
--
2.20.1


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