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Date: Thu, 23 Nov 2023 09:39:56 +0800
From: Wenchao Hao <haowenchao2@...wei.com>
To: Xiubo Li <xiubli@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
Jeff Layton <jlayton@...nel.org>,
Luis Henriques <lhenriques@...e.de>,
<ceph-devel@...r.kernel.org>
CC: <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ceph: quota: Fix invalid pointer access if
get_quota_realm return ERR_PTR
On 2023/11/22 12:29, Xiubo Li wrote:
>
> On 11/20/23 16:26, Wenchao Hao wrote:
>> This issue is reported by smatch that get_quota_realm() might return
>> ERR_PTR but we did not handle it. It's not a immediate bug, while we
>> still should address it to avoid potential bugs if get_quota_realm()
>> is changed to return other ERR_PTR in future.
>>
>> Set ceph_snap_realm's pointer in get_quota_realm()'s to address this
>> issue, the pointer would be set to NULL if get_quota_realm() failed
>> to get struct ceph_snap_realm, so no ERR_PTR would happen any more.
>>
>> Signed-off-by: Wenchao Hao <haowenchao2@...wei.com>
>> ---
>> V2:
>> - Fix all potential invalid pointer access caused by get_quota_realm
>> - Update commit comment and point it's not a immediate bug
>>
>> fs/ceph/quota.c | 41 +++++++++++++++++++++++------------------
>> 1 file changed, 23 insertions(+), 18 deletions(-)
>>
>> diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c
>> index 9d36c3532de1..e85a85b34a83 100644
>> --- a/fs/ceph/quota.c
>> +++ b/fs/ceph/quota.c
>> @@ -197,10 +197,10 @@ void ceph_cleanup_quotarealms_inodes(struct ceph_mds_client *mdsc)
>> }
>> /*
>> - * This function walks through the snaprealm for an inode and returns the
>> - * ceph_snap_realm for the first snaprealm that has quotas set (max_files,
>> + * This function walks through the snaprealm for an inode and set the
>> + * realmp with the first snaprealm that has quotas set (max_files,
>> * max_bytes, or any, depending on the 'which_quota' argument). If the root is
>> - * reached, return the root ceph_snap_realm instead.
>> + * reached, set the realmp with the root ceph_snap_realm instead.
>> *
>> * Note that the caller is responsible for calling ceph_put_snap_realm() on the
>> * returned realm.
>> @@ -211,10 +211,9 @@ void ceph_cleanup_quotarealms_inodes(struct ceph_mds_client *mdsc)
>> * this function will return -EAGAIN; otherwise, the snaprealms walk-through
>> * will be restarted.
>> */
>> -static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
>> - struct inode *inode,
>> - enum quota_get_realm which_quota,
>> - bool retry)
>> +static int get_quota_realm(struct ceph_mds_client *mdsc, struct inode *inode,
>> + enum quota_get_realm which_quota,
>> + struct ceph_snap_realm **realmp, bool retry)
>> {
>> struct ceph_client *cl = mdsc->fsc->client;
>> struct ceph_inode_info *ci = NULL;
>> @@ -222,8 +221,10 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
>> struct inode *in;
>> bool has_quota;
>> + if (realmp)
>> + *realmp = NULL;
>> if (ceph_snap(inode) != CEPH_NOSNAP)
>> - return NULL;
>> + return 0;
>> restart:
>> realm = ceph_inode(inode)->i_snap_realm;
>> @@ -250,7 +251,7 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
>> break;
>> ceph_put_snap_realm(mdsc, realm);
>> if (!retry)
>> - return ERR_PTR(-EAGAIN);
>> + return -EAGAIN;
>> goto restart;
>> }
>> @@ -259,8 +260,11 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
>> iput(in);
>> next = realm->parent;
>> - if (has_quota || !next)
>> - return realm;
>> + if (has_quota || !next) {
>> + if (realmp)
>> + *realmp = realm;
>> + return 0;
>> + }
>> ceph_get_snap_realm(mdsc, next);
>> ceph_put_snap_realm(mdsc, realm);
>> @@ -269,14 +273,15 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
>> if (realm)
>> ceph_put_snap_realm(mdsc, realm);
>> - return NULL;
>> + return 0;
>> }
>> bool ceph_quota_is_same_realm(struct inode *old, struct inode *new)
>> {
>> struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(old->i_sb);
>> - struct ceph_snap_realm *old_realm, *new_realm;
>> + struct ceph_snap_realm *old_realm = NULL, *new_realm = NULL;
>
> Here you initialized it as NULL.
>
>> bool is_same;
>> + int ret;
>> restart:
>> /*
>> @@ -286,9 +291,9 @@ bool ceph_quota_is_same_realm(struct inode *old, struct inode *new)
>> * dropped and we can then restart the whole operation.
>> */
>> down_read(&mdsc->snap_rwsem);
>> - old_realm = get_quota_realm(mdsc, old, QUOTA_GET_ANY, true);
>> - new_realm = get_quota_realm(mdsc, new, QUOTA_GET_ANY, false);
>> - if (PTR_ERR(new_realm) == -EAGAIN) {
>> + get_quota_realm(mdsc, old, QUOTA_GET_ANY, &old_realm, true);
>> + ret = get_quota_realm(mdsc, new, QUOTA_GET_ANY, &new_realm, false);
>> + if (ret == -EAGAIN) {
>> up_read(&mdsc->snap_rwsem);
>> if (old_realm)
>> ceph_put_snap_realm(mdsc, old_realm);
>> @@ -492,8 +497,8 @@ bool ceph_quota_update_statfs(struct ceph_fs_client *fsc, struct kstatfs *buf)
>> bool is_updated = false;
>> down_read(&mdsc->snap_rwsem);
>> - realm = get_quota_realm(mdsc, d_inode(fsc->sb->s_root),
>> - QUOTA_GET_MAX_BYTES, true);
>> + get_quota_realm(mdsc, d_inode(fsc->sb->s_root),
>> + QUOTA_GET_MAX_BYTES, &realm, true);
>
> While here you ignored it.
>
> I think we can just ignore it and the 'get_quota_realm()' will help initialize it.
Yes, I would remove the initialization in ceph_quota_is_same_realm() then repost.
>
> Thanks
>
> - Xiubo
>
>> up_read(&mdsc->snap_rwsem);
>> if (!realm)
>> return false;
>
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