2023-02-14 06:37:16

by Hangyu Hua

Subject: [PATCH v4] ksmbd: fix possible memory leak in smb2_lock()

argv needs to be free when setup_async_work fails or when the current
process is woken up.

Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Signed-off-by: Hangyu Hua <[email protected]>
---

v2: avoid NULL pointer dereference in set_close_state_blocked_works()
v3: avoid race condition between smb2_lock() and smb2_cancel()
v4: use another way to avoid race condition

fs/ksmbd/smb2pdu.c | 20 +++++++++++++-------
fs/ksmbd/vfs_cache.c | 2 ++
2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index d681f91947d9..1b517d3ca2ef 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -6666,7 +6666,8 @@ int smb2_cancel(struct ksmbd_work *work)
"smb2 with AsyncId %llu cancelled command = 0x%x\n",
le64_to_cpu(hdr->Id.AsyncId),
le16_to_cpu(chdr->Command));
- cancel_work = iter;
+ if (iter->cancel_fn)
+ cancel_work = iter;
break;
}
spin_unlock(&conn->request_lock);
@@ -7050,6 +7051,7 @@ int smb2_lock(struct ksmbd_work *work)
smb2_remove_blocked_lock,
argv);
if (rc) {
+ kfree(argv);
err = -ENOMEM;
goto out;
}
@@ -7061,6 +7063,16 @@ int smb2_lock(struct ksmbd_work *work)

ksmbd_vfs_posix_lock_wait(flock);

+ spin_lock(&work->conn->request_lock);
+ spin_lock(&fp->f_lock);
+ if (work->state != KSMBD_WORK_CLOSED) {
+ list_del(&work->fp_entry);
+ work->cancel_fn = NULL;
+ kfree(argv);
+ }
+ spin_unlock(&fp->f_lock);
+ spin_unlock(&work->conn->request_lock);
+
if (work->state != KSMBD_WORK_ACTIVE) {
list_del(&smb_lock->llist);
spin_lock(&work->conn->llist_lock);
@@ -7069,9 +7081,6 @@ int smb2_lock(struct ksmbd_work *work)
locks_free_lock(flock);

if (work->state == KSMBD_WORK_CANCELLED) {
- spin_lock(&fp->f_lock);
- list_del(&work->fp_entry);
- spin_unlock(&fp->f_lock);
rsp->hdr.Status =
STATUS_CANCELLED;
kfree(smb_lock);
@@ -7093,9 +7102,6 @@ int smb2_lock(struct ksmbd_work *work)
list_del(&smb_lock->clist);
spin_unlock(&work->conn->llist_lock);

- spin_lock(&fp->f_lock);
- list_del(&work->fp_entry);
- spin_unlock(&fp->f_lock);
goto retry;
} else if (!rc) {
spin_lock(&work->conn->llist_lock);
diff --git a/fs/ksmbd/vfs_cache.c b/fs/ksmbd/vfs_cache.c
index da9163b00350..761a8aa540ce 100644
--- a/fs/ksmbd/vfs_cache.c
+++ b/fs/ksmbd/vfs_cache.c
@@ -372,6 +372,8 @@ static void set_close_state_blocked_works(struct ksmbd_file *fp)
list_del(&cancel_work->fp_entry);
cancel_work->state = KSMBD_WORK_CLOSED;
cancel_work->cancel_fn(cancel_work->cancel_argv);
+ cancel_work->cancel_fn = NULL;
+ kfree(cancel_work->cancel_argv);
}
spin_unlock(&fp->f_lock);
}
--
2.34.1

2023-02-15 01:05:23

by Namjae Jeon

Subject: Re: [PATCH v4] ksmbd: fix possible memory leak in smb2_lock()

2023-02-14 15:36 GMT+09:00, Hangyu Hua <[email protected]>:
> argv needs to be free when setup_async_work fails or when the current
> process is woken up.
>
> Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
> Signed-off-by: Hangyu Hua <[email protected]>
> ---
>
> v2: avoid NULL pointer dereference in set_close_state_blocked_works()
> v3: avoid race condition between smb2_lock() and smb2_cancel()
> v4: use another way to avoid race condition
>
> fs/ksmbd/smb2pdu.c | 20 +++++++++++++-------
> fs/ksmbd/vfs_cache.c | 2 ++
> 2 files changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
> index d681f91947d9..1b517d3ca2ef 100644
> --- a/fs/ksmbd/smb2pdu.c
> +++ b/fs/ksmbd/smb2pdu.c
> @@ -6666,7 +6666,8 @@ int smb2_cancel(struct ksmbd_work *work)
> "smb2 with AsyncId %llu cancelled command = 0x%x\n",
> le64_to_cpu(hdr->Id.AsyncId),
> le16_to_cpu(chdr->Command));
> - cancel_work = iter;
> + if (iter->cancel_fn)
> + cancel_work = iter;
You have freed ->cancel_argv in smb2_lock(). Wouldn't this cause UAF
issue the below?

if (cancel_work) {
cancel_work->state = KSMBD_WORK_CANCELLED;
if (cancel_work->cancel_fn)
cancel_work->cancel_fn(cancel_work->cancel_argv);
}
> break;
> }
> spin_unlock(&conn->request_lock);
> @@ -7050,6 +7051,7 @@ int smb2_lock(struct ksmbd_work *work)
> smb2_remove_blocked_lock,
> argv);
> if (rc) {
> + kfree(argv);
> err = -ENOMEM;
> goto out;
> }
> @@ -7061,6 +7063,16 @@ int smb2_lock(struct ksmbd_work *work)
>
> ksmbd_vfs_posix_lock_wait(flock);
>
> + spin_lock(&work->conn->request_lock);
> + spin_lock(&fp->f_lock);
> + if (work->state != KSMBD_WORK_CLOSED) {
I think that this check is not needed if we don't delete entry in
set_close_state_blocked_works().
> + list_del(&work->fp_entry);
> + work->cancel_fn = NULL;
> + kfree(argv);
> + }
> + spin_unlock(&fp->f_lock);
> + spin_unlock(&work->conn->request_lock);
> +
> if (work->state != KSMBD_WORK_ACTIVE) {
> list_del(&smb_lock->llist);
> spin_lock(&work->conn->llist_lock);
> @@ -7069,9 +7081,6 @@ int smb2_lock(struct ksmbd_work *work)
> locks_free_lock(flock);
>
> if (work->state == KSMBD_WORK_CANCELLED) {
> - spin_lock(&fp->f_lock);
> - list_del(&work->fp_entry);
> - spin_unlock(&fp->f_lock);
> rsp->hdr.Status =
> STATUS_CANCELLED;
> kfree(smb_lock);
> @@ -7093,9 +7102,6 @@ int smb2_lock(struct ksmbd_work *work)
> list_del(&smb_lock->clist);
> spin_unlock(&work->conn->llist_lock);
>
> - spin_lock(&fp->f_lock);
> - list_del(&work->fp_entry);
> - spin_unlock(&fp->f_lock);
> goto retry;
> } else if (!rc) {
> spin_lock(&work->conn->llist_lock);
> diff --git a/fs/ksmbd/vfs_cache.c b/fs/ksmbd/vfs_cache.c
> index da9163b00350..761a8aa540ce 100644
> --- a/fs/ksmbd/vfs_cache.c
> +++ b/fs/ksmbd/vfs_cache.c
> @@ -372,6 +372,8 @@ static void set_close_state_blocked_works(struct
> ksmbd_file *fp)
> list_del(&cancel_work->fp_entry);
> cancel_work->state = KSMBD_WORK_CLOSED;
> cancel_work->cancel_fn(cancel_work->cancel_argv);
> + cancel_work->cancel_fn = NULL;
> + kfree(cancel_work->cancel_argv);
If we remove list_del, we don't need to do them here ? and we can
change _safe version to list_for_each().
> }
> spin_unlock(&fp->f_lock);
> }
> --
> 2.34.1
>
>

2023-02-15 04:45:28

by Hangyu Hua

Subject: Re: [PATCH v4] ksmbd: fix possible memory leak in smb2_lock()

On 15/2/2023 09:04, Namjae Jeon wrote:
> 2023-02-14 15:36 GMT+09:00, Hangyu Hua <[email protected]>:
>> argv needs to be free when setup_async_work fails or when the current
>> process is woken up.
>>
>> Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
>> Signed-off-by: Hangyu Hua <[email protected]>
>> ---
>>
>> v2: avoid NULL pointer dereference in set_close_state_blocked_works()
>> v3: avoid race condition between smb2_lock() and smb2_cancel()
>> v4: use another way to avoid race condition
>>
>> fs/ksmbd/smb2pdu.c | 20 +++++++++++++-------
>> fs/ksmbd/vfs_cache.c | 2 ++
>> 2 files changed, 15 insertions(+), 7 deletions(-)
>>
>> diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
>> index d681f91947d9..1b517d3ca2ef 100644
>> --- a/fs/ksmbd/smb2pdu.c
>> +++ b/fs/ksmbd/smb2pdu.c
>> @@ -6666,7 +6666,8 @@ int smb2_cancel(struct ksmbd_work *work)
>> "smb2 with AsyncId %llu cancelled command = 0x%x\n",
>> le64_to_cpu(hdr->Id.AsyncId),
>> le16_to_cpu(chdr->Command));
>> - cancel_work = iter;
>> + if (iter->cancel_fn)
>> + cancel_work = iter;
> You have freed ->cancel_argv in smb2_lock(). Wouldn't this cause UAF
> issue the below?
>
> if (cancel_work) {
> cancel_work->state = KSMBD_WORK_CANCELLED;
> if (cancel_work->cancel_fn)
> cancel_work->cancel_fn(cancel_work->cancel_argv);
> }
I think this can't cause UAF beacause cancel_fn will be set to NULL
before releasing argv in smb2_lock(). There is no way to use a argv.

>> break;
>> }
>> spin_unlock(&conn->request_lock);
>> @@ -7050,6 +7051,7 @@ int smb2_lock(struct ksmbd_work *work)
>> smb2_remove_blocked_lock,
>> argv);
>> if (rc) {
>> + kfree(argv);
>> err = -ENOMEM;
>> goto out;
>> }
>> @@ -7061,6 +7063,16 @@ int smb2_lock(struct ksmbd_work *work)
>>
>> ksmbd_vfs_posix_lock_wait(flock);
>>
>> + spin_lock(&work->conn->request_lock);
>> + spin_lock(&fp->f_lock);
>> + if (work->state != KSMBD_WORK_CLOSED) {
> I think that this check is not needed if we don't delete entry in
> set_close_state_blocked_works().
>> + list_del(&work->fp_entry);
>> + work->cancel_fn = NULL;
>> + kfree(argv);
>> + }
>> + spin_unlock(&fp->f_lock);
>> + spin_unlock(&work->conn->request_lock);
>> +
>> if (work->state != KSMBD_WORK_ACTIVE) {
>> list_del(&smb_lock->llist);
>> spin_lock(&work->conn->llist_lock);
>> @@ -7069,9 +7081,6 @@ int smb2_lock(struct ksmbd_work *work)
>> locks_free_lock(flock);
>>
>> if (work->state == KSMBD_WORK_CANCELLED) {
>> - spin_lock(&fp->f_lock);
>> - list_del(&work->fp_entry);
>> - spin_unlock(&fp->f_lock);
>> rsp->hdr.Status =
>> STATUS_CANCELLED;
>> kfree(smb_lock);
>> @@ -7093,9 +7102,6 @@ int smb2_lock(struct ksmbd_work *work)
>> list_del(&smb_lock->clist);
>> spin_unlock(&work->conn->llist_lock);
>>
>> - spin_lock(&fp->f_lock);
>> - list_del(&work->fp_entry);
>> - spin_unlock(&fp->f_lock);
>> goto retry;
>> } else if (!rc) {
>> spin_lock(&work->conn->llist_lock);
>> diff --git a/fs/ksmbd/vfs_cache.c b/fs/ksmbd/vfs_cache.c
>> index da9163b00350..761a8aa540ce 100644
>> --- a/fs/ksmbd/vfs_cache.c
>> +++ b/fs/ksmbd/vfs_cache.c
>> @@ -372,6 +372,8 @@ static void set_close_state_blocked_works(struct
>> ksmbd_file *fp)
>> list_del(&cancel_work->fp_entry);
>> cancel_work->state = KSMBD_WORK_CLOSED;
>> cancel_work->cancel_fn(cancel_work->cancel_argv);
>> + cancel_work->cancel_fn = NULL;
>> + kfree(cancel_work->cancel_argv);
> If we remove list_del, we don't need to do them here ? and we can
> change _safe version to list_for_each().

Agreed. I will move this list_del() to smb2_lock() in v5.

Thanks,
Hangyu

>> }
>> spin_unlock(&fp->f_lock);
>> }
>> --
>> 2.34.1
>>
>>

2023-02-16 14:18:43

by Namjae Jeon

Subject: Re: [PATCH v4] ksmbd: fix possible memory leak in smb2_lock()

2023-02-14 15:36 GMT+09:00, Hangyu Hua <[email protected]>:
> argv needs to be free when setup_async_work fails or when the current
> process is woken up.
>
> Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
> Signed-off-by: Hangyu Hua <[email protected]>
Acked-by: Namjae Jeon <[email protected]>

Thanks.