Re: [PATCH] ceph: fix cap ref leak via netfs init_request

[Xiubo Li]

On 10/3/24 09:05, Patrick Donnelly wrote:
> From: Patrick Donnelly <pdonnell@xxxxxxxxxx>
>
> Log recovered from a user's cluster:
>
>      <7>[ 5413.970692] ceph:  get_cap_refs 00000000958c114b ret 1 got Fr
>      <7>[ 5413.970695] ceph:  start_read 00000000958c114b, no cache cap
>      ...
>      <7>[ 5473.934609] ceph:   my wanted = Fr, used = Fr, dirty -
>      <7>[ 5473.934616] ceph:  revocation: pAsLsXsFr -> pAsLsXs (revoking Fr)
>      <7>[ 5473.934632] ceph:  __ceph_caps_issued 00000000958c114b cap 00000000f7784259 issued pAsLsXs
>      <7>[ 5473.934638] ceph:  check_caps 10000000e68.fffffffffffffffe file_want - used Fr dirty - flushing - issued pAsLsXs revoking Fr retain pAsLsXsFsr  AUTHONLY NOINVAL FLUSH_FORCE
>
> The MDS subsequently complains that the kernel client is late releasing caps.
>
> Approximately, a series of changes to this code by the three commits cited
> below resulted in subtle resource cleanup to be missed. The main culprit is the
> change in error handling in 2d31604 which meant that a failure in init_request
> would no longer cause cleanup to be called. That would prevent the
> ceph_put_cap_refs which would cleanup the leaked cap ref.
>
> Closes: https://tracker.ceph.com/issues/67008
> Fixes: 49870056005ca9387e5ee31451991491f99cc45f ("ceph: convert ceph_readpages to ceph_readahead")
> Fixes: 2de160417315b8d64455fe03e9bb7d3308ac3281 ("netfs: Change ->init_request() to return an error code")
> Fixes: a5c9dc4451394b2854493944dcc0ff71af9705a3 ("ceph: Make ceph_init_request() check caps on readahead")
> Signed-off-by: Patrick Donnelly <pdonnell@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>   fs/ceph/addr.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 53fef258c2bc..702c6a730b70 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -489,8 +489,11 @@ static int ceph_init_request(struct netfs_io_request *rreq, struct file *file)
>   	rreq->io_streams[0].sreq_max_len = fsc->mount_options->rsize;
>   
>   out:
> -	if (ret < 0)
> +	if (ret < 0) {
> +		if (got)
> +			ceph_put_cap_refs(ceph_inode(inode), got);
>   		kfree(priv);
> +	}
>   
>   	return ret;
>   }
>
> base-commit: e32cde8d2bd7d251a8f9b434143977ddf13dcec6

Good catch!

Reviewed-by: Xiubo Li <xiubli@xxxxxxxxxx>