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Subject[PATCH 02/13] f2fs: fix to avoid panic in dec_valid_node_count()
Date
As Jungyeon reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=203213

- Overview
When mounting the attached crafted image and running program, I got this error.
Additionally, it hangs on sync after running the this script.

The image is intentionally fuzzed from a normal f2fs image for testing and I enabled option CONFIG_F2FS_CHECK_FS on.

- Reproduces
mkdir test
mount -t f2fs tmp.img test
cp a.out test
cd test
sudo ./a.out
sync

kernel BUG at fs/f2fs/f2fs.h:2012!
RIP: 0010:truncate_node+0x2c9/0x2e0
Call Trace:
f2fs_truncate_xattr_node+0xa1/0x130
f2fs_remove_inode_page+0x82/0x2d0
f2fs_evict_inode+0x2a3/0x3a0
evict+0xba/0x180
__dentry_kill+0xbe/0x160
dentry_kill+0x46/0x180
dput+0xbb/0x100
do_renameat2+0x3c9/0x550
__x64_sys_rename+0x17/0x20
do_syscall_64+0x43/0xf0
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The reason is dec_valid_node_count() will trigger kernel panic due to
inconsistent count in between inode.i_blocks and actual block.

To avoid panic, let's just print debug message and set SBI_NEED_FSCK to
give a hint to fsck for latter repairing.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
fs/f2fs/f2fs.h | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 8952ce8f94b8..b98b22039f58 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2028,7 +2028,6 @@ static inline void dec_valid_node_count(struct f2fs_sb_info *sbi,

f2fs_bug_on(sbi, !sbi->total_valid_block_count);
f2fs_bug_on(sbi, !sbi->total_valid_node_count);
- f2fs_bug_on(sbi, !is_inode && !inode->i_blocks);

sbi->total_valid_node_count--;
sbi->total_valid_block_count--;
@@ -2038,10 +2037,18 @@ static inline void dec_valid_node_count(struct f2fs_sb_info *sbi,

spin_unlock(&sbi->stat_lock);

- if (is_inode)
+ if (is_inode) {
dquot_free_inode(inode);
- else
+ } else {
+ if (!inode->i_blocks) {
+ f2fs_msg(sbi->sb, KERN_WARNING,
+ "Inconsistent i_blocks, ino:%lu, iblocks:%zu",
+ inode->i_ino, inode->i_blocks);
+ set_sbi_flag(sbi, SBI_NEED_FSCK);
+ return;
+ }
f2fs_i_blocks_write(inode, 1, false, true);
+ }
}

static inline unsigned int valid_node_count(struct f2fs_sb_info *sbi)
--
2.18.0.rc1
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