summaryrefslogtreecommitdiff
path: root/fs/overlayfs
diff options
context:
space:
mode:
authorMiklos Szeredi <mszeredi@redhat.com>2020-03-27 18:51:02 +0300
committerMiklos Szeredi <mszeredi@redhat.com>2020-03-27 18:51:02 +0300
commit83552eacdfc06378b0993a3705833c1fd0aead4b (patch)
tree214cff1823d473697c1c56d7224987ab45295fd4 /fs/overlayfs
parenta5a84682ecb67e74d1f265d1634c146c990e0e4f (diff)
downloadlinux-83552eacdfc06378b0993a3705833c1fd0aead4b.tar.xz
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.c26
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) ||