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| author | Miklos Szeredi <mszeredi@redhat.com> | 2020-03-27 16:51:02 +0100 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-03-27 16:51:02 +0100 |
| commit | 83552eacdfc06378b0993a3705833c1fd0aead4b (patch) | |
| tree | 214cff1823d473697c1c56d7224987ab45295fd4 /fs/overlayfs | |
| parent | a5a84682ecb67e74d1f265d1634c146c990e0e4f (diff) | |
| download | lwn-83552eacdfc06378b0993a3705833c1fd0aead4b.tar.gz lwn-83552eacdfc06378b0993a3705833c1fd0aead4b.zip | |
ovl: fix WARN_ON nlink drop to zero
Changes to underlying layers should not cause WARN_ON(), but this repro
does:
mkdir w l u mnt
sudo mount -t overlay -o workdir=w,lowerdir=l,upperdir=u overlay mnt
touch mnt/h
ln u/h u/k
rm -rf mnt/k
rm -rf mnt/h
dmesg
------------[ cut here ]------------
WARNING: CPU: 1 PID: 116244 at fs/inode.c:302 drop_nlink+0x28/0x40
After upper hardlinks were added while overlay is mounted, unlinking all
overlay hardlinks drops overlay nlink to zero before all upper inodes
are unlinked.
After unlink/rename prevent i_nlink from going to zero if there are still
hashed aliases (i.e. cached hard links to the victim) remaining.
Reported-by: Phasip <phasip@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs')
| -rw-r--r-- | fs/overlayfs/dir.c | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index c91b5aae8e32..279009dee366 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -822,6 +822,28 @@ static bool ovl_pure_upper(struct dentry *dentry) !ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry)); } +static void ovl_drop_nlink(struct dentry *dentry) +{ + struct inode *inode = d_inode(dentry); + struct dentry *alias; + + /* Try to find another, hashed alias */ + spin_lock(&inode->i_lock); + hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) { + if (alias != dentry && !d_unhashed(alias)) + break; + } + spin_unlock(&inode->i_lock); + + /* + * Changes to underlying layers may cause i_nlink to lose sync with + * reality. In this case prevent the link count from going to zero + * prematurely. + */ + if (inode->i_nlink > !!alias) + drop_nlink(inode); +} + static int ovl_do_remove(struct dentry *dentry, bool is_dir) { int err; @@ -859,7 +881,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir) if (is_dir) clear_nlink(dentry->d_inode); else - drop_nlink(dentry->d_inode); + ovl_drop_nlink(dentry); } ovl_nlink_end(dentry); @@ -1204,7 +1226,7 @@ static int ovl_rename(struct inode *olddir, struct dentry *old, if (new_is_dir) clear_nlink(d_inode(new)); else - drop_nlink(d_inode(new)); + ovl_drop_nlink(new); } ovl_dir_modified(old->d_parent, ovl_type_origin(old) || |