On Thu, Nov 15, 2018 at 2:06 AM <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
>
> The patch below does not apply to the 4.18-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
Attached. Should apply to v4.14 as well.
Thanks,
Amir.
From 23a290ac1335544c2e74562f21feb5f838e192db Mon Sep 17 00:00:00 2001
From: Amir Goldstein <amir73il@xxxxxxxxx>
Date: Thu, 18 Oct 2018 09:45:49 +0300
Subject: [PATCH] ovl: fix recursive oi->lock in ovl_link()
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 5f8415d6b87e ("ovl: persistent overlay inode nlink for...")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.13
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
[amir: backport to v4.18]
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/dir.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index d00e66b2a047..36847411c118 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -661,6 +661,11 @@ static int ovl_link(struct dentry *old, struct inode *newdir,
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;
--
2.7.4
