[PATCH] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

[PATCH] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

[Eremin, Dmitry]

In the original commit 4d99b2581effe115376402e710fbcb1c3c073769
was missed one hunk. Added it now to avoid issue with use after free.

Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
---
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
index 2ebc484..a15a625 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
@@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
 		atomic_dec(&net->ibn_nconns);
 	}
 
-	kfree(conn);
+	if (free_conn)
+		kfree(conn);
 }
 
 int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)
-- 
1.8.3.1


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Re: [PATCH] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

[Greg Kroah-Hartman]

On Tue, Jan 16, 2018 at 03:01:49PM +0000, Eremin, Dmitry wrote:
> In the original commit 4d99b2581effe115376402e710fbcb1c3c073769

Please use the documented way to write this:
	4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")

> was missed one hunk. Added it now to avoid issue with use after free.

And I do not understand this commit message at all.

> 
> Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
> ---
>  drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> index 2ebc484..a15a625 100644
> --- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> +++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> @@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
>  		atomic_dec(&net->ibn_nconns);
>  	}
>  
> -	kfree(conn);
> +	if (free_conn)
> +		kfree(conn);

This looks really odd, don't you think?

thanks,

greg k-h

Re: [PATCH] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

[Dilger, Andreas]

> On Jan 16, 2018, at 09:56, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> 
> On Tue, Jan 16, 2018 at 03:01:49PM +0000, Eremin, Dmitry wrote:
>> In the original commit 4d99b2581effe115376402e710fbcb1c3c073769
> 
> Please use the documented way to write this:
> 	4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
> 

>> was missed one hunk. Added it now to avoid issue with use after free.
> 
> And I do not understand this commit message at all.
> 
>> Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
>> ---
>> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
>> index 2ebc484..a15a625 100644
>> --- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
>> +++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
>> @@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
>> 		atomic_dec(&net->ibn_nconns);
>> 	}
>> 
>> -	kfree(conn);
>> +	if (free_conn)
>> +		kfree(conn);
> 
> This looks really odd, don't you think?

I'm not sure what the objection is here?  There is an argument to this
this function named "free_conn" which determines if the structure should
be freed, or if the network connection is just being torn down and
reconnected.

Cheers, Andreas
--
Andreas Dilger
Lustre Principal Architect
Intel Corporation

Re: [PATCH] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

[Greg Kroah-Hartman]

On Wed, Jan 17, 2018 at 12:36:19AM +0000, Dilger, Andreas wrote:
> 
> > On Jan 16, 2018, at 09:56, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> > 
> > On Tue, Jan 16, 2018 at 03:01:49PM +0000, Eremin, Dmitry wrote:
> >> In the original commit 4d99b2581effe115376402e710fbcb1c3c073769
> > 
> > Please use the documented way to write this:
> > 	4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
> > 
> 
> >> was missed one hunk. Added it now to avoid issue with use after free.
> > 
> > And I do not understand this commit message at all.
> > 
> >> Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
> >> ---
> >> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >> 
> >> diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> >> index 2ebc484..a15a625 100644
> >> --- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> >> +++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> >> @@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
> >> 		atomic_dec(&net->ibn_nconns);
> >> 	}
> >> 
> >> -	kfree(conn);
> >> +	if (free_conn)
> >> +		kfree(conn);
> > 
> > This looks really odd, don't you think?
> 
> I'm not sure what the objection is here?  There is an argument to this
> this function named "free_conn" which determines if the structure should
> be freed, or if the network connection is just being torn down and
> reconnected.

At first glance it really looks like the normal pattern of:
	if (foo_ptr)
		kfree(foo_ptr);

right?

If you don't want to free the variable, set it to NULL.

Even then, this is a horrible function, you should have 2 different
ones:
	kiblnd_destroy_conn(...)
	kiblnd_free_conn()

and then just free the variable in the free_conn() function if you were
going to set the free_conn variable, right?

That way no odd code paths are taken, and it's obvious what you are
doing just by reading the code at the callsite.

thanks,

greg k-h

[PATCH] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

[Eremin, Dmitry]

The logic of the original commit 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
was assumed conditional free of struct kib_conn if the second argument free_conn in function
kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn) is true. But this hunk of code was dropped
from original commit. As result the logic works wrong and current code use struct kib_conn after
free.

> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
>   3317                          kiblnd_destroy_conn(conn, !peer);
>                                                     ^^^^ Freed always (but should be conditionally)
>   3318
>   3319                          spin_lock_irqsave(lock, flags);
>   3320                          if (!peer)
>   3321                                  continue;
>   3322
>   3323                          conn->ibc_peer = peer;
>                                     ^^^^^^^^^^^^^ Use after free
>   3324                          if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
>   3325                                  list_add_tail(&conn->ibc_list,
>                                                                        ^^^^^^^^^^^^
>   3326                                                &kiblnd_data.kib_reconn_list);
>   3327                          else
>   3328                                  list_add_tail(&conn->ibc_list,
>                                                                         ^^^^^^^^^^^^
>   3329                                                &kiblnd_data.kib_reconn_wait);

After attached patch this code will use struct kib_conn only when it was not freed.

Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
---
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
index 2ebc484..a15a625 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
@@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
 		atomic_dec(&net->ibn_nconns);
 	}
 
-	kfree(conn);
+	if (free_conn)
+		kfree(conn);
 }
 
 int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)
-- 
1.8.3.1


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Re: [PATCH] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

[Greg Kroah-Hartman]

On Tue, Jan 16, 2018 at 06:02:07PM +0000, Eremin, Dmitry wrote:
> The logic of the original commit 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
> was assumed conditional free of struct kib_conn if the second argument free_conn in function
> kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn) is true. But this hunk of code was dropped
> from original commit. As result the logic works wrong and current code use struct kib_conn after
> free.
> 
> > drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
> >   3317                          kiblnd_destroy_conn(conn, !peer);
> >                                                     ^^^^ Freed always (but should be conditionally)
> >   3318
> >   3319                          spin_lock_irqsave(lock, flags);
> >   3320                          if (!peer)
> >   3321                                  continue;
> >   3322
> >   3323                          conn->ibc_peer = peer;
> >                                     ^^^^^^^^^^^^^ Use after free
> >   3324                          if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
> >   3325                                  list_add_tail(&conn->ibc_list,
> >                                                                        ^^^^^^^^^^^^
> >   3326                                                &kiblnd_data.kib_reconn_list);
> >   3327                          else
> >   3328                                  list_add_tail(&conn->ibc_list,
> >                                                                         ^^^^^^^^^^^^
> >   3329                                                &kiblnd_data.kib_reconn_wait);
> 
> After attached patch this code will use struct kib_conn only when it was not freed.
> 
> Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
> ---
>  drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> index 2ebc484..a15a625 100644
> --- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> +++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> @@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
>  		atomic_dec(&net->ibn_nconns);
>  	}
>  
> -	kfree(conn);
> +	if (free_conn)
> +		kfree(conn);
>  }
>  
>  int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)

This patch needs a real "Fixes:" tag, right?

Also, as this was from 4.6, it should go to the stable trees, right?
Can you resend this with that info, and then send a follow-on patch to
fix this up the way I recommended so that no one is confused in the
future?

thanks,

greg k-h

[PATCH v2] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

[Dmitry Eremin]

From: Dmitry Eremin <Dmitry.Eremin@intel.com>

The logic of the original commit 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
was assumed conditional free of struct kib_conn if the second argument free_conn
in function kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn) is true.
But this hunk of code was dropped from original commit. As result the logic
works wrong and current code use struct kib_conn after free.

> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
> 3317  kiblnd_destroy_conn(conn, !peer);
>                           ^^^^ Freed always (but should be conditionally)
> 3318
> 3319  spin_lock_irqsave(lock, flags);
> 3320  if (!peer)
> 3321      continue;
> 3322
> 3323  conn->ibc_peer = peer;
>       ^^^^^^^^^^^^^^ Use after free
> 3324  if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
> 3325      list_add_tail(&conn->ibc_list,
>                          ^^^^^^^^^^^^^^ Use after free
> 3326                    &kiblnd_data.kib_reconn_list);
> 3327  else
> 3328      list_add_tail(&conn->ibc_list,
>                          ^^^^^^^^^^^^^^ Use after free
> 3329                    &kiblnd_data.kib_reconn_wait);

After attached patch this code will use struct kib_conn only when it was not freed.

Cc: <stable@vger.kernel.org> # v4.6
Fixes: 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
---
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
index 2ebc484385b3..a15a625ee9b6 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
@@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
 		atomic_dec(&net->ibn_nconns);
 	}
 
-	kfree(conn);
+	if (free_conn)
+		kfree(conn);
 }
 
 int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)
-- 
1.8.3.1


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[PATCH v3] staging: lustre: separate a connection destroy from free struct kib_conn

[Dmitry Eremin]

Rewrite the logic of the original commit 4d99b2581eff ("staging: lustre: avoid
intensive reconnecting for ko2iblnd") and move the freeing a struct kib_conn
outside of the function kiblnd_destroy_conn(). The freeing of struct kib_conn
should be depending on the second argument free_conn of function
kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn). If it true the
structure should be freed.

Fixes: 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
---
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c    | 7 +++----
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h    | 2 +-
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c | 6 ++++--
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
index 2ebc484385b3..ec84edfda271 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
@@ -824,14 +824,15 @@ struct kib_conn *kiblnd_create_conn(struct kib_peer *peer, struct rdma_cm_id *cm
 	return conn;
 
  failed_2:
-	kiblnd_destroy_conn(conn, true);
+	kiblnd_destroy_conn(conn);
+	kfree(conn);
  failed_1:
 	kfree(init_qp_attr);
  failed_0:
 	return NULL;
 }
 
-void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
+void kiblnd_destroy_conn(struct kib_conn *conn)
 {
 	struct rdma_cm_id *cmid = conn->ibc_cmid;
 	struct kib_peer *peer = conn->ibc_peer;
@@ -889,8 +890,6 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
 		rdma_destroy_id(cmid);
 		atomic_dec(&net->ibn_nconns);
 	}
-
-	kfree(conn);
 }
 
 int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)
diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
index 171eced213f8..b18911d09e9a 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
@@ -1016,7 +1016,7 @@ int  kiblnd_close_stale_conns_locked(struct kib_peer *peer,
 struct kib_conn *kiblnd_create_conn(struct kib_peer *peer,
 				    struct rdma_cm_id *cmid,
 				    int state, int version);
-void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn);
+void kiblnd_destroy_conn(struct kib_conn *conn);
 void kiblnd_close_conn(struct kib_conn *conn, int error);
 void kiblnd_close_conn_locked(struct kib_conn *conn, int error);
 
diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
index 9b3328c5d1e7..b3e7f28eb978 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
@@ -3314,11 +3314,13 @@ static int kiblnd_resolve_addr(struct rdma_cm_id *cmid,
 			spin_unlock_irqrestore(lock, flags);
 			dropped_lock = 1;
 
-			kiblnd_destroy_conn(conn, !peer);
+			kiblnd_destroy_conn(conn);
 
 			spin_lock_irqsave(lock, flags);
-			if (!peer)
+			if (!peer) {
+				kfree(conn);
 				continue;
+			}
 
 			conn->ibc_peer = peer;
 			if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
-- 
1.8.3.1


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Re: [PATCH v3] staging: lustre: separate a connection destroy from free struct kib_conn

[Greg Kroah-Hartman]

On Wed, Jan 24, 2018 at 05:14:12PM +0300, Dmitry Eremin wrote:
> Rewrite the logic of the original commit 4d99b2581eff ("staging: lustre: avoid
> intensive reconnecting for ko2iblnd") and move the freeing a struct kib_conn
> outside of the function kiblnd_destroy_conn(). The freeing of struct kib_conn
> should be depending on the second argument free_conn of function
> kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn). If it true the
> structure should be freed.
> 
> Fixes: 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
> Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
> ---
>  drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c    | 7 +++----
>  drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h    | 2 +-
>  drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c | 6 ++++--
>  3 files changed, 8 insertions(+), 7 deletions(-)

What changed from version 2 and 1?  Always included that below the ---
line please.

4th try is a charm?  :)

thanks,

greg k-h
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[PATCH v4] staging: lustre: separate a connection destroy from free struct kib_conn

[Dmitry Eremin]

The logic of the original commit 4d99b2581eff ("staging: lustre: avoid
intensive reconnecting for ko2iblnd") was assumed conditional free of
struct kib_conn if the second argument free_conn in function
kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn) is true.
But this hunk of code was dropped from original commit. As result the logic
works wrong and current code use struct kib_conn after free.

> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
> 3317  kiblnd_destroy_conn(conn, !peer);
>                           ^^^^ Freed always (but should be conditionally)
> 3318
> 3319  spin_lock_irqsave(lock, flags);
> 3320  if (!peer)
> 3321      continue;
> 3322
> 3323  conn->ibc_peer = peer;
>       ^^^^^^^^^^^^^^ Use after free
> 3324  if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
> 3325      list_add_tail(&conn->ibc_list,
>                          ^^^^^^^^^^^^^^ Use after free
> 3326                    &kiblnd_data.kib_reconn_list);
> 3327  else
> 3328      list_add_tail(&conn->ibc_list,
>                          ^^^^^^^^^^^^^^ Use after free
> 3329                    &kiblnd_data.kib_reconn_wait);

To avoid confusion this fix moved the freeing a struct kib_conn outside of
the function kiblnd_destroy_conn() and free as it was intended in original
commit.

Cc: <stable@vger.kernel.org> # v4.6
Fixes: 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
---
Changes in v4:
    - fixed the issue with use after free by moving the freeing a struct
      kib_conn outside of the function kiblnd_destroy_conn()

 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c    | 7 +++----
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h    | 2 +-
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c | 6 ++++--
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
index 2ebc484385b3..ec84edfda271 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
@@ -824,14 +824,15 @@ struct kib_conn *kiblnd_create_conn(struct kib_peer *peer, struct rdma_cm_id *cm
 	return conn;
 
  failed_2:
-	kiblnd_destroy_conn(conn, true);
+	kiblnd_destroy_conn(conn);
+	kfree(conn);
  failed_1:
 	kfree(init_qp_attr);
  failed_0:
 	return NULL;
 }
 
-void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
+void kiblnd_destroy_conn(struct kib_conn *conn)
 {
 	struct rdma_cm_id *cmid = conn->ibc_cmid;
 	struct kib_peer *peer = conn->ibc_peer;
@@ -889,8 +890,6 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
 		rdma_destroy_id(cmid);
 		atomic_dec(&net->ibn_nconns);
 	}
-
-	kfree(conn);
 }
 
 int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)
diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
index 171eced213f8..b18911d09e9a 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
@@ -1016,7 +1016,7 @@ int  kiblnd_close_stale_conns_locked(struct kib_peer *peer,
 struct kib_conn *kiblnd_create_conn(struct kib_peer *peer,
 				    struct rdma_cm_id *cmid,
 				    int state, int version);
-void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn);
+void kiblnd_destroy_conn(struct kib_conn *conn);
 void kiblnd_close_conn(struct kib_conn *conn, int error);
 void kiblnd_close_conn_locked(struct kib_conn *conn, int error);
 
diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
index 9b3328c5d1e7..b3e7f28eb978 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
@@ -3314,11 +3314,13 @@ static int kiblnd_resolve_addr(struct rdma_cm_id *cmid,
 			spin_unlock_irqrestore(lock, flags);
 			dropped_lock = 1;
 
-			kiblnd_destroy_conn(conn, !peer);
+			kiblnd_destroy_conn(conn);
 
 			spin_lock_irqsave(lock, flags);
-			if (!peer)
+			if (!peer) {
+				kfree(conn);
 				continue;
+			}
 
 			conn->ibc_peer = peer;
 			if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
-- 
1.8.3.1


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Re: [PATCH v4] staging: lustre: separate a connection destroy from free struct kib_conn

[Dilger, Andreas]

On Jan 25, 2018, at 06:51, Eremin, Dmitry <dmitry.eremin@intel.com> wrote:
> 
> The logic of the original commit 4d99b2581eff ("staging: lustre: avoid
> intensive reconnecting for ko2iblnd") was assumed conditional free of
> struct kib_conn if the second argument free_conn in function
> kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn) is true.
> But this hunk of code was dropped from original commit. As result the logic
> works wrong and current code use struct kib_conn after free.
> 
>> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
>> 3317  kiblnd_destroy_conn(conn, !peer);
>>                          ^^^^ Freed always (but should be conditionally)
>> 3318
>> 3319  spin_lock_irqsave(lock, flags);
>> 3320  if (!peer)
>> 3321      continue;
>> 3322
>> 3323  conn->ibc_peer = peer;
>>      ^^^^^^^^^^^^^^ Use after free
>> 3324  if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
>> 3325      list_add_tail(&conn->ibc_list,
>>                         ^^^^^^^^^^^^^^ Use after free
>> 3326                    &kiblnd_data.kib_reconn_list);
>> 3327  else
>> 3328      list_add_tail(&conn->ibc_list,
>>                         ^^^^^^^^^^^^^^ Use after free
>> 3329                    &kiblnd_data.kib_reconn_wait);
> 
> To avoid confusion this fix moved the freeing a struct kib_conn outside of
> the function kiblnd_destroy_conn() and free as it was intended in original
> commit.
> 
> Cc: <stable@vger.kernel.org> # v4.6
> Fixes: 4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
> Signed-off-by: Dmitry Eremin <Dmitry.Eremin@intel.com>

Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>

> ---
> Changes in v4:
>    - fixed the issue with use after free by moving the freeing a struct
>      kib_conn outside of the function kiblnd_destroy_conn()
> 
> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c    | 7 +++----
> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h    | 2 +-
> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c | 6 ++++--
> 3 files changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> index 2ebc484385b3..ec84edfda271 100644
> --- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> +++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
> @@ -824,14 +824,15 @@ struct kib_conn *kiblnd_create_conn(struct kib_peer *peer, struct rdma_cm_id *cm
> 	return conn;
> 
>  failed_2:
> -	kiblnd_destroy_conn(conn, true);
> +	kiblnd_destroy_conn(conn);
> +	kfree(conn);
>  failed_1:
> 	kfree(init_qp_attr);
>  failed_0:
> 	return NULL;
> }
> 
> -void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
> +void kiblnd_destroy_conn(struct kib_conn *conn)
> {
> 	struct rdma_cm_id *cmid = conn->ibc_cmid;
> 	struct kib_peer *peer = conn->ibc_peer;
> @@ -889,8 +890,6 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
> 		rdma_destroy_id(cmid);
> 		atomic_dec(&net->ibn_nconns);
> 	}
> -
> -	kfree(conn);
> }
> 
> int kiblnd_close_peer_conns_locked(struct kib_peer *peer, int why)
> diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
> index 171eced213f8..b18911d09e9a 100644
> --- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
> +++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.h
> @@ -1016,7 +1016,7 @@ int  kiblnd_close_stale_conns_locked(struct kib_peer *peer,
> struct kib_conn *kiblnd_create_conn(struct kib_peer *peer,
> 				    struct rdma_cm_id *cmid,
> 				    int state, int version);
> -void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn);
> +void kiblnd_destroy_conn(struct kib_conn *conn);
> void kiblnd_close_conn(struct kib_conn *conn, int error);
> void kiblnd_close_conn_locked(struct kib_conn *conn, int error);
> 
> diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
> index 9b3328c5d1e7..b3e7f28eb978 100644
> --- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
> +++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
> @@ -3314,11 +3314,13 @@ static int kiblnd_resolve_addr(struct rdma_cm_id *cmid,
> 			spin_unlock_irqrestore(lock, flags);
> 			dropped_lock = 1;
> 
> -			kiblnd_destroy_conn(conn, !peer);
> +			kiblnd_destroy_conn(conn);
> 
> 			spin_lock_irqsave(lock, flags);
> -			if (!peer)
> +			if (!peer) {
> +				kfree(conn);
> 				continue;
> +			}
> 
> 			conn->ibc_peer = peer;
> 			if (peer->ibp_reconnected < KIB_RECONN_HIGH_RACE)
> -- 
> 1.8.3.1
> 

Cheers, Andreas
--
Andreas Dilger
Lustre Principal Architect
Intel Corporation