4.18-stable review patch. If anyone has any objections, please let me know.
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From: Amir Goldstein amir73il@gmail.com
commit 6cd078702f2f33cb6b19a682de3e9184112f1a46 upstream.
linking a non-copied-up file into a non-copied-up parent results in a nested call to mutex_lock_interruptible(&oi->lock). Fix this by copying up target parent before ovl_nlink_start(), same as done in ovl_rename().
~/unionmount-testsuite$ ./run --ov -s ~/unionmount-testsuite$ ln /mnt/a/foo100 /mnt/a/dir100/
WARNING: possible recursive locking detected -------------------------------------------- ln/1545 is trying to acquire lock: 00000000bcce7c4c (&ovl_i_lock_key[depth]){+.+.}, at: ovl_copy_up_start+0x28/0x7d but task is already holding lock: 0000000026d73d5b (&ovl_i_lock_key[depth]){+.+.}, at: ovl_nlink_start+0x3c/0xc1
[SzM: this seems to be a false positive, but doing the copy-up first is harmless and removes the lockdep splat]
Reported-by: syzbot+3ef5c0d1a5cb0b21e6be@syzkaller.appspotmail.com Fixes: 5f8415d6b87e ("ovl: persistent overlay inode nlink for...") Cc: stable@vger.kernel.org # v4.13 Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com [amir: backport to v4.18] Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/overlayfs/dir.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -665,6 +665,11 @@ static int ovl_link(struct dentry *old, if (err) goto out_drop_write;
+ err = ovl_copy_up(new->d_parent); + if (err) + goto out_drop_write; + + err = ovl_nlink_start(old, &locked); if (err) goto out_drop_write;