[PATCH v3 0/6] Bluetooth: Fix potential double free caused by hci_conn_unlink

[PATCH v3 0/6] Bluetooth: Fix potential double free caused by hci_conn_unlink

[Ruihan Li]

This patch series contains six fixes related to hci_conn_unlink. The
purpose is to prevent merge conflicts between each other. I'm not
intentially linking them together. So if any patch is not suitable,
please just let me know (I'll be grateful if you can explain the
reason).

The first three patches are the most important, each fixing a
triggerable use-after-free bug (see the report URL for details). And the
fourth through sixth patches are a bit more minor, containing mostly
tweaks and refactorings.

Changes since v2:
  * Put all fixes, adjustments, and refactorings about hci_conn_unlink
    in one patch series.
Link to v2:
  * https://lore.kernel.org/linux-bluetooth/20230430180535.168270-1-lrh2000@pku.edu.cn/
See also:
  * https://lore.kernel.org/linux-bluetooth/20230430171847.156825-1-lrh2000@pku.edu.cn/

Changes since v1:
  * Resolve merge conflicts.
Link to v1:
  * https://lore.kernel.org/linux-bluetooth/20230430172937.157999-1-lrh2000@pku.edu.cn/

Ruihan Li (6):
  Bluetooth: Fix potential double free caused by hci_conn_unlink
  Bluetooth: Refcnt drop must be placed last in hci_conn_unlink
  Bluetooth: Fix UAF in hci_conn_hash_flush again
  Bluetooth: Perform hci_conn_drop in hci_conn_unlink
  Bluetooth: Unlink CISes when LE disconnects in hci_conn_del
  Bluetooth: Avoid recursion in hci_conn_unlink

 include/net/bluetooth/hci_core.h |  2 +-
 net/bluetooth/hci_conn.c         | 96 ++++++++++++++++++--------------
 2 files changed, 54 insertions(+), 44 deletions(-)

-- 
2.40.0

[PATCH v3 1/6] Bluetooth: Fix potential double free caused by hci_conn_unlink

[Ruihan Li]

The hci_conn_unlink function is being called by hci_conn_del, which
means it should not call hci_conn_del with the input parameter conn
again. If it does, conn may have already been released when
hci_conn_unlink returns, leading to potential UAF and double-free
issues.

This patch resolves the problem by modifying hci_conn_unlink to release
only conn's child links when necessary, but never release conn itself.

Reported-by: syzbot+690b90b14f14f43f4688@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-bluetooth/000000000000484a8205faafe216@google.com/
Fixes: 06149746e720 ("Bluetooth: hci_conn: Add support for linking multiple hcon")
Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
---
 net/bluetooth/hci_conn.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 640b951bf..70e1655a9 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1083,8 +1083,18 @@ static void hci_conn_unlink(struct hci_conn *conn)
 	if (!conn->parent) {
 		struct hci_link *link, *t;
 
-		list_for_each_entry_safe(link, t, &conn->link_list, list)
-			hci_conn_unlink(link->conn);
+		list_for_each_entry_safe(link, t, &conn->link_list, list) {
+			struct hci_conn *child = link->conn;
+
+			hci_conn_unlink(child);
+
+			/* Due to race, SCO connection might be not established
+			 * yet at this point. Delete it now, otherwise it is
+			 * possible for it to be stuck and can't be deleted.
+			 */
+			if (child->handle == HCI_CONN_HANDLE_UNSET)
+				hci_conn_del(child);
+		}
 
 		return;
 	}
@@ -1100,13 +1110,6 @@ static void hci_conn_unlink(struct hci_conn *conn)
 
 	kfree(conn->link);
 	conn->link = NULL;
-
-	/* Due to race, SCO connection might be not established
-	 * yet at this point. Delete it now, otherwise it is
-	 * possible for it to be stuck and can't be deleted.
-	 */
-	if (conn->handle == HCI_CONN_HANDLE_UNSET)
-		hci_conn_del(conn);
 }
 
 int hci_conn_del(struct hci_conn *conn)
-- 
2.40.0

RE: Bluetooth: Fix potential double free caused by hci_conn_unlink

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 8849 bytes --]

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=744426

---Test result---

Test Summary:
CheckPatch                    FAIL      4.18 seconds
GitLint                       FAIL      2.05 seconds
SubjectPrefix                 PASS      0.60 seconds
BuildKernel                   PASS      32.22 seconds
CheckAllWarning               PASS      35.05 seconds
CheckSparse                   PASS      39.69 seconds
CheckSmatch                   PASS      110.75 seconds
BuildKernel32                 PASS      31.05 seconds
TestRunnerSetup               PASS      440.47 seconds
TestRunner_l2cap-tester       PASS      16.56 seconds
TestRunner_iso-tester         PASS      20.35 seconds
TestRunner_bnep-tester        PASS      5.36 seconds
TestRunner_mgmt-tester        PASS      113.08 seconds
TestRunner_rfcomm-tester      PASS      8.52 seconds
TestRunner_sco-tester         PASS      7.90 seconds
TestRunner_ioctl-tester       PASS      9.26 seconds
TestRunner_mesh-tester        PASS      6.76 seconds
TestRunner_smp-tester         PASS      7.93 seconds
TestRunner_userchan-tester    PASS      5.61 seconds
IncrementalBuild              PASS      75.99 seconds

Details
##############################
Test: CheckPatch - FAIL
Desc: Run checkpatch.pl script
Output:
[v3,1/6] Bluetooth: Fix potential double free caused by hci_conn_unlink
WARNING: Reported-by: should be immediately followed by Link: with a URL to the report
#83: 
Reported-by: syzbot+690b90b14f14f43f4688@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-bluetooth/000000000000484a8205faafe216@google.com/

WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#84: 
Closes: https://lore.kernel.org/linux-bluetooth/000000000000484a8205faafe216@google.com/

WARNING: Unknown link reference 'Closes:', use 'Link:' instead
#84: 
Closes: https://lore.kernel.org/linux-bluetooth/000000000000484a8205faafe216@google.com/

total: 0 errors, 3 warnings, 0 checks, 33 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

/github/workspace/src/src/13229025.patch has style problems, please review.

NOTE: Ignored message types: UNKNOWN_COMMIT_ID

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.


[v3,2/6] Bluetooth: Refcnt drop must be placed last in hci_conn_unlink
WARNING: Reported-by: should be immediately followed by Link: with a URL to the report
#82: 
Reported-by: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Closes: https://lore.kernel.org/linux-bluetooth/CABBYNZ+1kce8_RJrLNOXd_8=Mdpb=2bx4Nto-hFORk=qiOkoCg@mail.gmail.com/

WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#83: 
Closes: https://lore.kernel.org/linux-bluetooth/CABBYNZ+1kce8_RJrLNOXd_8=Mdpb=2bx4Nto-hFORk=qiOkoCg@mail.gmail.com/

WARNING: Unknown link reference 'Closes:', use 'Link:' instead
#83: 
Closes: https://lore.kernel.org/linux-bluetooth/CABBYNZ+1kce8_RJrLNOXd_8=Mdpb=2bx4Nto-hFORk=qiOkoCg@mail.gmail.com/

total: 0 errors, 3 warnings, 0 checks, 15 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

/github/workspace/src/src/13229023.patch has style problems, please review.

NOTE: Ignored message types: UNKNOWN_COMMIT_ID

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.


[v3,3/6] Bluetooth: Fix UAF in hci_conn_hash_flush again
WARNING: Reported-by: should be immediately followed by Link: with a URL to the report
#93: 
Reported-by: syzbot+8bb72f86fc823817bc5d@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-bluetooth/000000000000aa920505f60d25ad@google.com/

WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#94: 
Closes: https://lore.kernel.org/linux-bluetooth/000000000000aa920505f60d25ad@google.com/

WARNING: Unknown link reference 'Closes:', use 'Link:' instead
#94: 
Closes: https://lore.kernel.org/linux-bluetooth/000000000000aa920505f60d25ad@google.com/

total: 0 errors, 3 warnings, 0 checks, 58 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

/github/workspace/src/src/13229024.patch has style problems, please review.

NOTE: Ignored message types: UNKNOWN_COMMIT_ID

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.


##############################
Test: GitLint - FAIL
Desc: Run gitlint
Output:
[v3,1/6] Bluetooth: Fix potential double free caused by hci_conn_unlink

WARNING: I3 - ignore-body-lines: gitlint will be switching from using Python regex 'match' (match beginning) to 'search' (match anywhere) semantics. Please review your ignore-body-lines.regex option accordingly. To remove this warning, set general.regex-style-search=True. More details: https://jorisroovers.github.io/gitlint/configuration/#regex-style-search
13: B1 Line exceeds max length (88>80): "Closes: https://lore.kernel.org/linux-bluetooth/000000000000484a8205faafe216@google.com/"
[v3,2/6] Bluetooth: Refcnt drop must be placed last in hci_conn_unlink

WARNING: I3 - ignore-body-lines: gitlint will be switching from using Python regex 'match' (match beginning) to 'search' (match anywhere) semantics. Please review your ignore-body-lines.regex option accordingly. To remove this warning, set general.regex-style-search=True. More details: https://jorisroovers.github.io/gitlint/configuration/#regex-style-search
13: B1 Line exceeds max length (115>80): "Closes: https://lore.kernel.org/linux-bluetooth/CABBYNZ+1kce8_RJrLNOXd_8=Mdpb=2bx4Nto-hFORk=qiOkoCg@mail.gmail.com/"
[v3,3/6] Bluetooth: Fix UAF in hci_conn_hash_flush again

WARNING: I3 - ignore-body-lines: gitlint will be switching from using Python regex 'match' (match beginning) to 'search' (match anywhere) semantics. Please review your ignore-body-lines.regex option accordingly. To remove this warning, set general.regex-style-search=True. More details: https://jorisroovers.github.io/gitlint/configuration/#regex-style-search
24: B1 Line exceeds max length (88>80): "Closes: https://lore.kernel.org/linux-bluetooth/000000000000aa920505f60d25ad@google.com/"
[v3,4/6] Bluetooth: Perform hci_conn_drop in hci_conn_unlink

WARNING: I3 - ignore-body-lines: gitlint will be switching from using Python regex 'match' (match beginning) to 'search' (match anywhere) semantics. Please review your ignore-body-lines.regex option accordingly. To remove this warning, set general.regex-style-search=True. More details: https://jorisroovers.github.io/gitlint/configuration/#regex-style-search
13: B3 Line contains hard tab characters (\t): "	hci_conn_unlink(conn)  [conn->parent == NULL]"
14: B3 Line contains hard tab characters (\t): "		-> hci_conn_unlink(child)  [child->parent == conn]"
15: B3 Line contains hard tab characters (\t): "			-> hci_conn_drop(child->parent)"
16: B3 Line contains hard tab characters (\t): "				-> queue_delayed_work(&conn->disc_work)"
[v3,5/6] Bluetooth: Unlink CISes when LE disconnects in hci_conn_del

WARNING: I3 - ignore-body-lines: gitlint will be switching from using Python regex 'match' (match beginning) to 'search' (match anywhere) semantics. Please review your ignore-body-lines.regex option accordingly. To remove this warning, set general.regex-style-search=True. More details: https://jorisroovers.github.io/gitlint/configuration/#regex-style-search
13: B3 Line contains hard tab characters (\t): "	All SCO, eSCO, and CIS connections on a physical link should be"
14: B3 Line contains hard tab characters (\t): "	disconnected before the ACL connection on the same physical"
15: B3 Line contains hard tab characters (\t): "	connection is disconnected. If it does not, they will be"
16: B3 Line contains hard tab characters (\t): "	implicitly disconnected as part of the ACL disconnection."
17: B3 Line contains hard tab characters (\t): "	..."
18: B3 Line contains hard tab characters (\t): "	Note: As specified in Section 7.7.5, on the Central, the handle"
19: B3 Line contains hard tab characters (\t): "	for a CIS remains valid even after disconnection and, therefore,"
20: B3 Line contains hard tab characters (\t): "	the Host can recreate a disconnected CIS at a later point in"
21: B3 Line contains hard tab characters (\t): "	time using the same connection handle."


---
Regards,
Linux Bluetooth

[PATCH v3 2/6] Bluetooth: Refcnt drop must be placed last in hci_conn_unlink

[Ruihan Li]

If hci_conn_put(conn->parent) reduces conn->parent's reference count to
zero, it can immediately deallocate conn->parent. At the same time,
conn->link->list has its head in conn->parent, causing use-after-free
problems in the latter list_del_rcu(&conn->link->list).

This problem can be easily solved by reordering the two operations,
i.e., first performing the list removal with list_del_rcu and then
decreasing the refcnt with hci_conn_put.

Reported-by: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Closes: https://lore.kernel.org/linux-bluetooth/CABBYNZ+1kce8_RJrLNOXd_8=Mdpb=2bx4Nto-hFORk=qiOkoCg@mail.gmail.com/
Fixes: 06149746e720 ("Bluetooth: hci_conn: Add support for linking multiple hcon")
Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
---
 net/bluetooth/hci_conn.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 70e1655a9..44d0643fc 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1102,12 +1102,12 @@ static void hci_conn_unlink(struct hci_conn *conn)
 	if (!conn->link)
 		return;
 
-	hci_conn_put(conn->parent);
-	conn->parent = NULL;
-
 	list_del_rcu(&conn->link->list);
 	synchronize_rcu();
 
+	hci_conn_put(conn->parent);
+	conn->parent = NULL;
+
 	kfree(conn->link);
 	conn->link = NULL;
 }
-- 
2.40.0

[PATCH v3 3/6] Bluetooth: Fix UAF in hci_conn_hash_flush again

[Ruihan Li]

Commit 06149746e720 ("Bluetooth: hci_conn: Add support for linking
multiple hcon") reintroduced a previously fixed bug [1] ("KASAN:
slab-use-after-free Read in hci_conn_hash_flush"). This bug was
originally fixed by commit 5dc7d23e167e ("Bluetooth: hci_conn: Fix
possible UAF").

The hci_conn_unlink function was added to avoid invalidating the link
traversal caused by successive hci_conn_del operations releasing extra
connections. However, currently hci_conn_unlink itself also releases
extra connections, resulted in the reintroduced bug.

This patch follows a more robust solution for cleaning up all
connections, by repeatedly removing the first connection until there are
none left. This approach does not rely on the inner workings of
hci_conn_del and ensures proper cleanup of all connections.

Meanwhile, we need to make sure that hci_conn_del never fails. Indeed it
doesn't, as it now always returns zero. To make this a bit clearer, this
patch also changes its return type to void.

Reported-by: syzbot+8bb72f86fc823817bc5d@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-bluetooth/000000000000aa920505f60d25ad@google.com/
Fixes: 06149746e720 ("Bluetooth: hci_conn: Add support for linking multiple hcon")
Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
---
 include/net/bluetooth/hci_core.h |  2 +-
 net/bluetooth/hci_conn.c         | 29 +++++++++++++----------------
 2 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index a6c8aee2f..8baf34639 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -1327,7 +1327,7 @@ int hci_le_create_cis(struct hci_conn *conn);
 
 struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
 			      u8 role);
-int hci_conn_del(struct hci_conn *conn);
+void hci_conn_del(struct hci_conn *conn);
 void hci_conn_hash_flush(struct hci_dev *hdev);
 void hci_conn_check_pending(struct hci_dev *hdev);
 
diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 44d0643fc..eef148291 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1112,7 +1112,7 @@ static void hci_conn_unlink(struct hci_conn *conn)
 	conn->link = NULL;
 }
 
-int hci_conn_del(struct hci_conn *conn)
+void hci_conn_del(struct hci_conn *conn)
 {
 	struct hci_dev *hdev = conn->hdev;
 
@@ -1163,8 +1163,6 @@ int hci_conn_del(struct hci_conn *conn)
 	 * rest of hci_conn_del.
 	 */
 	hci_conn_cleanup(conn);
-
-	return 0;
 }
 
 struct hci_dev *hci_get_route(bdaddr_t *dst, bdaddr_t *src, uint8_t src_type)
@@ -2465,22 +2463,21 @@ void hci_conn_enter_active_mode(struct hci_conn *conn, __u8 force_active)
 /* Drop all connection on the device */
 void hci_conn_hash_flush(struct hci_dev *hdev)
 {
-	struct hci_conn_hash *h = &hdev->conn_hash;
-	struct hci_conn *c, *n;
+	struct list_head *head = &hdev->conn_hash.list;
+	struct hci_conn *conn;
 
 	BT_DBG("hdev %s", hdev->name);
 
-	list_for_each_entry_safe(c, n, &h->list, list) {
-		c->state = BT_CLOSED;
-
-		hci_disconn_cfm(c, HCI_ERROR_LOCAL_HOST_TERM);
-
-		/* Unlink before deleting otherwise it is possible that
-		 * hci_conn_del removes the link which may cause the list to
-		 * contain items already freed.
-		 */
-		hci_conn_unlink(c);
-		hci_conn_del(c);
+	/* We should not traverse the list here, because hci_conn_del
+	 * can remove extra links, which may cause the list traversal
+	 * to hit items that have already been released.
+	 */
+	while ((conn = list_first_entry_or_null(head,
+						struct hci_conn,
+						list)) != NULL) {
+		conn->state = BT_CLOSED;
+		hci_disconn_cfm(conn, HCI_ERROR_LOCAL_HOST_TERM);
+		hci_conn_del(conn);
 	}
 }
 
-- 
2.40.0

[PATCH v3 4/6] Bluetooth: Perform hci_conn_drop in hci_conn_unlink

[Ruihan Li]

Since hci_conn_link invokes both hci_conn_get and hci_conn_hold,
hci_conn_unlink should perform both hci_conn_put and hci_conn_drop as
well. However, currently it performs only hci_conn_put.

This patch makes hci_conn_unlink call hci_conn_drop as well, which
simplifies the logic in hci_conn_del a bit and may benefit future users
of hci_conn_unlink. But it is noted that this change additionally
implies that hci_conn_unlink can queue disc_work on conn itself, with
the following call stack:

	hci_conn_unlink(conn)  [conn->parent == NULL]
		-> hci_conn_unlink(child)  [child->parent == conn]
			-> hci_conn_drop(child->parent)
				-> queue_delayed_work(&conn->disc_work)

Queued disc_work after hci_conn_del can be spurious, so during the
process of hci_conn_del, it is necessary to make the call to
cancel_delayed_work(&conn->disc_work) after invoking hci_conn_unlink.

Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
---
 net/bluetooth/hci_conn.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index eef148291..e76ebb50d 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1105,6 +1105,7 @@ static void hci_conn_unlink(struct hci_conn *conn)
 	list_del_rcu(&conn->link->list);
 	synchronize_rcu();
 
+	hci_conn_drop(conn->parent);
 	hci_conn_put(conn->parent);
 	conn->parent = NULL;
 
@@ -1118,7 +1119,6 @@ void hci_conn_del(struct hci_conn *conn)
 
 	BT_DBG("%s hcon %p handle %d", hdev->name, conn, conn->handle);
 
-	cancel_delayed_work_sync(&conn->disc_work);
 	cancel_delayed_work_sync(&conn->auto_accept_work);
 	cancel_delayed_work_sync(&conn->idle_work);
 
@@ -1134,12 +1134,7 @@ void hci_conn_del(struct hci_conn *conn)
 		else
 			hdev->acl_cnt += conn->sent;
 	} else {
-		struct hci_conn *acl = conn->parent;
-
-		if (acl) {
-			hci_conn_unlink(conn);
-			hci_conn_drop(acl);
-		}
+		hci_conn_unlink(conn);
 
 		/* Unacked ISO frames */
 		if (conn->type == ISO_LINK) {
@@ -1152,6 +1147,11 @@ void hci_conn_del(struct hci_conn *conn)
 		}
 	}
 
+	/* hci_conn_unlink may trigger additional disc_work, so
+	 * ensure to perform cancelling after that.
+	 */
+	cancel_delayed_work_sync(&conn->disc_work);
+
 	if (conn->amp_mgr)
 		amp_mgr_put(conn->amp_mgr);
 
-- 
2.40.0

Re: [PATCH v3 4/6] Bluetooth: Perform hci_conn_drop in hci_conn_unlink

[Luiz Augusto von Dentz]

Hi Ruihan,

On Tue, May 2, 2023 at 7:57 AM Ruihan Li <lrh2000@pku.edu.cn> wrote:
>
> Since hci_conn_link invokes both hci_conn_get and hci_conn_hold,
> hci_conn_unlink should perform both hci_conn_put and hci_conn_drop as
> well. However, currently it performs only hci_conn_put.
>
> This patch makes hci_conn_unlink call hci_conn_drop as well, which
> simplifies the logic in hci_conn_del a bit and may benefit future users
> of hci_conn_unlink. But it is noted that this change additionally
> implies that hci_conn_unlink can queue disc_work on conn itself, with
> the following call stack:
>
>         hci_conn_unlink(conn)  [conn->parent == NULL]
>                 -> hci_conn_unlink(child)  [child->parent == conn]
>                         -> hci_conn_drop(child->parent)
>                                 -> queue_delayed_work(&conn->disc_work)
>
> Queued disc_work after hci_conn_del can be spurious, so during the
> process of hci_conn_del, it is necessary to make the call to
> cancel_delayed_work(&conn->disc_work) after invoking hci_conn_unlink.
>
> Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
> ---
>  net/bluetooth/hci_conn.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> index eef148291..e76ebb50d 100644
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -1105,6 +1105,7 @@ static void hci_conn_unlink(struct hci_conn *conn)
>         list_del_rcu(&conn->link->list);
>         synchronize_rcu();
>
> +       hci_conn_drop(conn->parent);
>         hci_conn_put(conn->parent);
>         conn->parent = NULL;
>
> @@ -1118,7 +1119,6 @@ void hci_conn_del(struct hci_conn *conn)
>
>         BT_DBG("%s hcon %p handle %d", hdev->name, conn, conn->handle);
>
> -       cancel_delayed_work_sync(&conn->disc_work);
>         cancel_delayed_work_sync(&conn->auto_accept_work);
>         cancel_delayed_work_sync(&conn->idle_work);
>
> @@ -1134,12 +1134,7 @@ void hci_conn_del(struct hci_conn *conn)
>                 else
>                         hdev->acl_cnt += conn->sent;
>         } else {
> -               struct hci_conn *acl = conn->parent;
> -
> -               if (acl) {
> -                       hci_conn_unlink(conn);
> -                       hci_conn_drop(acl);
> -               }
> +               hci_conn_unlink(conn);
>
>                 /* Unacked ISO frames */
>                 if (conn->type == ISO_LINK) {
> @@ -1152,6 +1147,11 @@ void hci_conn_del(struct hci_conn *conn)
>                 }
>         }
>
> +       /* hci_conn_unlink may trigger additional disc_work, so
> +        * ensure to perform cancelling after that.
> +        */
> +       cancel_delayed_work_sync(&conn->disc_work);

Just merge the change where hci_conn_del calls hci_conn_unlink
unconditionally so we don't have to do this change independently just
to revert later.

>         if (conn->amp_mgr)
>                 amp_mgr_put(conn->amp_mgr);
>
> --
> 2.40.0
>


-- 
Luiz Augusto von Dentz

[PATCH v3 5/6] Bluetooth: Unlink CISes when LE disconnects in hci_conn_del

[Ruihan Li]

Currently, hci_conn_del calls hci_conn_unlink for BR/EDR, (e)SCO, and
CIS connections, i.e., everything except LE connections. However, if
(e)SCO connections are unlinked when BR/EDR disconnects, CIS connections
should also be unlinked when LE disconnects.

In terms of disconnection behavior, CIS and (e)SCO connections are not
too different. One peculiarity of CIS is that when CIS connections are
disconnected, the CIS handle isn't deleted, as per [BLUETOOTH CORE
SPECIFICATION Version 5.4 | Vol 4, Part E] 7.1.6 Disconnect command:

	All SCO, eSCO, and CIS connections on a physical link should be
	disconnected before the ACL connection on the same physical
	connection is disconnected. If it does not, they will be
	implicitly disconnected as part of the ACL disconnection.
	...
	Note: As specified in Section 7.7.5, on the Central, the handle
	for a CIS remains valid even after disconnection and, therefore,
	the Host can recreate a disconnected CIS at a later point in
	time using the same connection handle.

This peculiarity has nothing to do with the code, as long as the current
implementation always ties the CIS handle, the CIS connection, and the
LE connection together in hci_link, and manually performs CIS deletion
in cis_cleanup after CIS disconnections.

Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
---
 net/bluetooth/hci_conn.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index e76ebb50d..de553e062 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1092,7 +1092,9 @@ static void hci_conn_unlink(struct hci_conn *conn)
 			 * yet at this point. Delete it now, otherwise it is
 			 * possible for it to be stuck and can't be deleted.
 			 */
-			if (child->handle == HCI_CONN_HANDLE_UNSET)
+			if ((child->type == SCO_LINK ||
+			     child->type == ESCO_LINK) &&
+			    child->handle == HCI_CONN_HANDLE_UNSET)
 				hci_conn_del(child);
 		}
 
@@ -1119,11 +1121,17 @@ void hci_conn_del(struct hci_conn *conn)
 
 	BT_DBG("%s hcon %p handle %d", hdev->name, conn, conn->handle);
 
+	hci_conn_unlink(conn);
+
+	/* hci_conn_unlink may trigger additional disc_work, so
+	 * ensure to perform cancelling after that.
+	 */
+	cancel_delayed_work_sync(&conn->disc_work);
+
 	cancel_delayed_work_sync(&conn->auto_accept_work);
 	cancel_delayed_work_sync(&conn->idle_work);
 
 	if (conn->type == ACL_LINK) {
-		hci_conn_unlink(conn);
 		/* Unacked frames */
 		hdev->acl_cnt += conn->sent;
 	} else if (conn->type == LE_LINK) {
@@ -1134,8 +1142,6 @@ void hci_conn_del(struct hci_conn *conn)
 		else
 			hdev->acl_cnt += conn->sent;
 	} else {
-		hci_conn_unlink(conn);
-
 		/* Unacked ISO frames */
 		if (conn->type == ISO_LINK) {
 			if (hdev->iso_pkts)
@@ -1147,11 +1153,6 @@ void hci_conn_del(struct hci_conn *conn)
 		}
 	}
 
-	/* hci_conn_unlink may trigger additional disc_work, so
-	 * ensure to perform cancelling after that.
-	 */
-	cancel_delayed_work_sync(&conn->disc_work);
-
 	if (conn->amp_mgr)
 		amp_mgr_put(conn->amp_mgr);
 
-- 
2.40.0

[PATCH v3 6/6] Bluetooth: Avoid recursion in hci_conn_unlink

[Ruihan Li]

Previously, hci_conn_unlink was implemented as a recursion function. To
unlink physical connections (e.g. ACL/LE), it calls itself to unlink all
its logical channels (e.g. SCO/eSCO/ISO).

Recursion is not required. This patch refactors hci_conn_unlink into two
functions, where hci_conn_unlink_parent takes a physical connection,
checks out all its logical channels, and calls hci_conn_unlink_child for
each logical channel to unlink it.

Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
---
 net/bluetooth/hci_conn.c | 55 +++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 23 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index de553e062..243d68a64 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1074,34 +1074,13 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
 	return conn;
 }
 
-static void hci_conn_unlink(struct hci_conn *conn)
+static void hci_conn_unlink_parent(struct hci_conn *conn)
 {
 	struct hci_dev *hdev = conn->hdev;
 
 	bt_dev_dbg(hdev, "hcon %p", conn);
 
-	if (!conn->parent) {
-		struct hci_link *link, *t;
-
-		list_for_each_entry_safe(link, t, &conn->link_list, list) {
-			struct hci_conn *child = link->conn;
-
-			hci_conn_unlink(child);
-
-			/* Due to race, SCO connection might be not established
-			 * yet at this point. Delete it now, otherwise it is
-			 * possible for it to be stuck and can't be deleted.
-			 */
-			if ((child->type == SCO_LINK ||
-			     child->type == ESCO_LINK) &&
-			    child->handle == HCI_CONN_HANDLE_UNSET)
-				hci_conn_del(child);
-		}
-
-		return;
-	}
-
-	if (!conn->link)
+	if (WARN_ON(!conn->link))
 		return;
 
 	list_del_rcu(&conn->link->list);
@@ -1115,6 +1094,36 @@ static void hci_conn_unlink(struct hci_conn *conn)
 	conn->link = NULL;
 }
 
+static void hci_conn_unlink_children(struct hci_conn *conn)
+{
+	struct hci_dev *hdev = conn->hdev;
+	struct hci_link *link, *t;
+
+	bt_dev_dbg(hdev, "hcon %p", conn);
+
+	list_for_each_entry_safe(link, t, &conn->link_list, list) {
+		struct hci_conn *child = link->conn;
+
+		hci_conn_unlink_parent(child);
+
+		/* Due to race, SCO connection might be not established
+		 * yet at this point. Delete it now, otherwise it is
+		 * possible for it to be stuck and can't be deleted.
+		 */
+		if (child->type == SCO_LINK || child->type == ESCO_LINK)
+			if (child->handle == HCI_CONN_HANDLE_UNSET)
+				hci_conn_del(child);
+	}
+}
+
+static void hci_conn_unlink(struct hci_conn *conn)
+{
+	if (conn->parent)
+		hci_conn_unlink_parent(conn);
+	else
+		hci_conn_unlink_children(conn);
+}
+
 void hci_conn_del(struct hci_conn *conn)
 {
 	struct hci_dev *hdev = conn->hdev;
-- 
2.40.0

Re: [PATCH v3 6/6] Bluetooth: Avoid recursion in hci_conn_unlink

[Luiz Augusto von Dentz]

Hi Ruihan,

On Tue, May 2, 2023 at 7:57 AM Ruihan Li <lrh2000@pku.edu.cn> wrote:
>
> Previously, hci_conn_unlink was implemented as a recursion function. To
> unlink physical connections (e.g. ACL/LE), it calls itself to unlink all
> its logical channels (e.g. SCO/eSCO/ISO).
>
> Recursion is not required. This patch refactors hci_conn_unlink into two
> functions, where hci_conn_unlink_parent takes a physical connection,
> checks out all its logical channels, and calls hci_conn_unlink_child for
> each logical channel to unlink it.
>
> Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
> ---
>  net/bluetooth/hci_conn.c | 55 +++++++++++++++++++++++-----------------
>  1 file changed, 32 insertions(+), 23 deletions(-)
>
> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> index de553e062..243d68a64 100644
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -1074,34 +1074,13 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
>         return conn;
>  }
>
> -static void hci_conn_unlink(struct hci_conn *conn)
> +static void hci_conn_unlink_parent(struct hci_conn *conn)
>  {
>         struct hci_dev *hdev = conn->hdev;
>
>         bt_dev_dbg(hdev, "hcon %p", conn);
>
> -       if (!conn->parent) {
> -               struct hci_link *link, *t;
> -
> -               list_for_each_entry_safe(link, t, &conn->link_list, list) {
> -                       struct hci_conn *child = link->conn;
> -
> -                       hci_conn_unlink(child);
> -
> -                       /* Due to race, SCO connection might be not established
> -                        * yet at this point. Delete it now, otherwise it is
> -                        * possible for it to be stuck and can't be deleted.
> -                        */
> -                       if ((child->type == SCO_LINK ||
> -                            child->type == ESCO_LINK) &&
> -                           child->handle == HCI_CONN_HANDLE_UNSET)
> -                               hci_conn_del(child);
> -               }
> -
> -               return;
> -       }
> -
> -       if (!conn->link)
> +       if (WARN_ON(!conn->link))
>                 return;
>
>         list_del_rcu(&conn->link->list);
> @@ -1115,6 +1094,36 @@ static void hci_conn_unlink(struct hci_conn *conn)
>         conn->link = NULL;
>  }
>
> +static void hci_conn_unlink_children(struct hci_conn *conn)
> +{
> +       struct hci_dev *hdev = conn->hdev;
> +       struct hci_link *link, *t;
> +
> +       bt_dev_dbg(hdev, "hcon %p", conn);
> +
> +       list_for_each_entry_safe(link, t, &conn->link_list, list) {
> +               struct hci_conn *child = link->conn;
> +
> +               hci_conn_unlink_parent(child);
> +
> +               /* Due to race, SCO connection might be not established
> +                * yet at this point. Delete it now, otherwise it is
> +                * possible for it to be stuck and can't be deleted.
> +                */
> +               if (child->type == SCO_LINK || child->type == ESCO_LINK)
> +                       if (child->handle == HCI_CONN_HANDLE_UNSET)
> +                               hci_conn_del(child);
> +       }

This is not quite right, when we are unlinking the children's hci_conn
it shall only unlink itself from the parent not everything.

> +}
> +
> +static void hci_conn_unlink(struct hci_conn *conn)
> +{
> +       if (conn->parent)
> +               hci_conn_unlink_parent(conn);
> +       else
> +               hci_conn_unlink_children(conn);
> +}
> +
>  void hci_conn_del(struct hci_conn *conn)
>  {
>         struct hci_dev *hdev = conn->hdev;
> --
> 2.40.0
>


-- 
Luiz Augusto von Dentz

Re: [PATCH v3 6/6] Bluetooth: Avoid recursion in hci_conn_unlink

[Ruihan Li]

Hi Luiz,

On Tue, May 02, 2023 at 09:18:02AM -0700, Luiz Augusto von Dentz wrote:
> Hi Ruihan,
> 
> On Tue, May 2, 2023 at 7:57 AM Ruihan Li <lrh2000@pku.edu.cn> wrote:
> >
> > Previously, hci_conn_unlink was implemented as a recursion function. To
> > unlink physical connections (e.g. ACL/LE), it calls itself to unlink all
> > its logical channels (e.g. SCO/eSCO/ISO).
> >
> > Recursion is not required. This patch refactors hci_conn_unlink into two
> > functions, where hci_conn_unlink_parent takes a physical connection,
> > checks out all its logical channels, and calls hci_conn_unlink_child for
> > each logical channel to unlink it.
> >
> > Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
> > ---
> >  net/bluetooth/hci_conn.c | 55 +++++++++++++++++++++++-----------------
> >  1 file changed, 32 insertions(+), 23 deletions(-)
> >
> > diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> > index de553e062..243d68a64 100644
> > --- a/net/bluetooth/hci_conn.c
> > +++ b/net/bluetooth/hci_conn.c
> > @@ -1074,34 +1074,13 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
> >         return conn;
> >  }
> >
> > -static void hci_conn_unlink(struct hci_conn *conn)
> > +static void hci_conn_unlink_parent(struct hci_conn *conn)
> >  {
> >         struct hci_dev *hdev = conn->hdev;
> >
> >         bt_dev_dbg(hdev, "hcon %p", conn);
> >
> > -       if (!conn->parent) {
> > -               struct hci_link *link, *t;
> > -
> > -               list_for_each_entry_safe(link, t, &conn->link_list, list) {
> > -                       struct hci_conn *child = link->conn;
> > -
> > -                       hci_conn_unlink(child);
> > -
> > -                       /* Due to race, SCO connection might be not established
> > -                        * yet at this point. Delete it now, otherwise it is
> > -                        * possible for it to be stuck and can't be deleted.
> > -                        */
> > -                       if ((child->type == SCO_LINK ||
> > -                            child->type == ESCO_LINK) &&
> > -                           child->handle == HCI_CONN_HANDLE_UNSET)
> > -                               hci_conn_del(child);
> > -               }
> > -
> > -               return;
> > -       }
> > -
> > -       if (!conn->link)
> > +       if (WARN_ON(!conn->link))
> >                 return;
> >
> >         list_del_rcu(&conn->link->list);
> > @@ -1115,6 +1094,36 @@ static void hci_conn_unlink(struct hci_conn *conn)
> >         conn->link = NULL;
> >  }
> >
> > +static void hci_conn_unlink_children(struct hci_conn *conn)
> > +{
> > +       struct hci_dev *hdev = conn->hdev;
> > +       struct hci_link *link, *t;
> > +
> > +       bt_dev_dbg(hdev, "hcon %p", conn);
> > +
> > +       list_for_each_entry_safe(link, t, &conn->link_list, list) {
> > +               struct hci_conn *child = link->conn;
> > +
> > +               hci_conn_unlink_parent(child);
> > +
> > +               /* Due to race, SCO connection might be not established
> > +                * yet at this point. Delete it now, otherwise it is
> > +                * possible for it to be stuck and can't be deleted.
> > +                */
> > +               if (child->type == SCO_LINK || child->type == ESCO_LINK)
> > +                       if (child->handle == HCI_CONN_HANDLE_UNSET)
> > +                               hci_conn_del(child);
> > +       }
> 
> This is not quite right, when we are unlinking the children's hci_conn
> it shall only unlink itself from the parent not everything.

My assumption is that each hci_conn is either
 * a logical channel, which implies that it has a parent and no
   children, or
 * a physical link, which means that it has no parent and possibly some
   children.
So here, as children of physical links, they must be logical channels
and thus cannot have more children, so just unlinking them from the
parent should be ok. We can add some assertions like
	WARN_ON(!conn->parent || !conn->link)   // conn has a parent
	WARN_ON(!list_empty(&conn->link_list))  // conn has no children
in hci_conn_unlink_parent.

Do you think this assumption is wrong, or could become wrong in the
future? Otherwise, I don't think there are correctness problems.

In my opinion, separating the functions for logical channels and
physical links makes the code a bit cleaner. But it's my opinion, if you
think it actually makes the code harder to understand, I won't insist.

> 
> > +}
> > +
> > +static void hci_conn_unlink(struct hci_conn *conn)
> > +{
> > +       if (conn->parent)
> > +               hci_conn_unlink_parent(conn);
> > +       else
> > +               hci_conn_unlink_children(conn);
> > +}
> > +
> >  void hci_conn_del(struct hci_conn *conn)
> >  {
> >         struct hci_dev *hdev = conn->hdev;
> > --
> > 2.40.0
> >
> 
> 
> -- 
> Luiz Augusto von Dentz

Thanks,
Ruihan Li

[PATCH] Bluetooth: Fix potential double free caused by hci_conn_unlink

[Ruihan Li]

The hci_conn_unlink function is being called by hci_conn_del, which means
it should not call hci_conn_del with the input parameter conn again. If it
does, conn may have already been released when hci_conn_unlink returns,
leading to potential UAF and double-free issues.

This patch resolves the problem by modifying hci_conn_unlink to release
only conn's child links when necessary, but never release conn itself.

Fixes: 06149746e720 ("Bluetooth: hci_conn: Add support for linking multiple hcon")
Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
---
 net/bluetooth/hci_conn.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 85c34c837..5f388202f 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1083,8 +1083,18 @@ static void hci_conn_unlink(struct hci_conn *conn)
 	if (!conn->parent) {
 		struct hci_link *link, *t;
 
-		list_for_each_entry_safe(link, t, &conn->link_list, list)
-			hci_conn_unlink(link->conn);
+		list_for_each_entry_safe(link, t, &conn->link_list, list) {
+			struct hci_conn *child = link->conn;
+
+			hci_conn_unlink(child);
+
+			/* Due to race, SCO connection might be not established
+			 * yet at this point. Delete it now, otherwise it is
+			 * possible for it to be stuck and can't be deleted.
+			 */
+			if (child->handle == HCI_CONN_HANDLE_UNSET)
+				hci_conn_del(child);
+		}
 
 		return;
 	}
@@ -1100,13 +1110,6 @@ static void hci_conn_unlink(struct hci_conn *conn)
 
 	kfree(conn->link);
 	conn->link = NULL;
-
-	/* Due to race, SCO connection might be not established
-	 * yet at this point. Delete it now, otherwise it is
-	 * possible for it to be stuck and can't be deleted.
-	 */
-	if (conn->handle == HCI_CONN_HANDLE_UNSET)
-		hci_conn_del(conn);
 }
 
 void hci_conn_del(struct hci_conn *conn)
-- 
2.40.0

RE: Bluetooth: Fix potential double free caused by hci_conn_unlink

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 551 bytes --]

This is an automated email and please do not reply to this email.

Dear Submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
While preparing the CI tests, the patches you submitted couldn't be applied to the current HEAD of the repository.

----- Output -----

error: patch failed: net/bluetooth/hci_conn.c:1100
error: net/bluetooth/hci_conn.c: patch does not apply
hint: Use 'git am --show-current-patch' to see the failed patch

Please resolve the issue and submit the patches again.


---
Regards,
Linux Bluetooth