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Subject[PATCH 4.18 074/168] ceph: avoid a use-after-free in ceph_destroy_options()
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ilya Dryomov <idryomov@gmail.com>

[ Upstream commit 8aaff15168cfbc7c8980fdb0e8a585f1afe56ec0 ]

syzbot reported a use-after-free in ceph_destroy_options(), called from
ceph_mount(). The problem was that create_fs_client() consumed the opt
pointer on some errors, but not on all of them. Make sure it always
consumes both libceph and ceph options.

Reported-by: syzbot+8ab6f1042021b4eed062@syzkaller.appspotmail.com
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ceph/super.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -603,6 +603,8 @@ static int extra_mon_dispatch(struct cep

/*
* create a new fs client
+ *
+ * Success or not, this function consumes @fsopt and @opt.
*/
static struct ceph_fs_client *create_fs_client(struct ceph_mount_options *fsopt,
struct ceph_options *opt)
@@ -610,17 +612,20 @@ static struct ceph_fs_client *create_fs_
struct ceph_fs_client *fsc;
int page_count;
size_t size;
- int err = -ENOMEM;
+ int err;

fsc = kzalloc(sizeof(*fsc), GFP_KERNEL);
- if (!fsc)
- return ERR_PTR(-ENOMEM);
+ if (!fsc) {
+ err = -ENOMEM;
+ goto fail;
+ }

fsc->client = ceph_create_client(opt, fsc);
if (IS_ERR(fsc->client)) {
err = PTR_ERR(fsc->client);
goto fail;
}
+ opt = NULL; /* fsc->client now owns this */

fsc->client->extra_mon_dispatch = extra_mon_dispatch;
fsc->client->osdc.abort_on_full = true;
@@ -678,6 +683,9 @@ fail_client:
ceph_destroy_client(fsc->client);
fail:
kfree(fsc);
+ if (opt)
+ ceph_destroy_options(opt);
+ destroy_mount_options(fsopt);
return ERR_PTR(err);
}

@@ -1042,8 +1050,6 @@ static struct dentry *ceph_mount(struct
fsc = create_fs_client(fsopt, opt);
if (IS_ERR(fsc)) {
res = ERR_CAST(fsc);
- destroy_mount_options(fsopt);
- ceph_destroy_options(opt);
goto out_final;
}


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