Re: #syz test

Re: #syz test

[syzbot]

> #syz test git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> master
>
> From d5153b84b90fa80ee0d041d1bd28bd465f7913ec Mon Sep 17 00:00:00 2001
> From: Masahiro Kawada <youjingxiaogao2@gmail.com>
> Date: Mon, 9 Feb 2026 04:47:14 +0900
> Subject: [PATCH] Bluetooth: fix use-after-free in hci_conn_drop
>
> Fix a use-after-free in hci_conn_drop triggered via hci_cmd_sync_work.
>
> In hci_conn_del(), hci_cmd_sync_dequeue() is called after
> hci_conn_cleanup() which may have already freed the conn pointer.
> Fix by moving the dequeue before cleanup.
>
> Additionally, le_read_features_complete() calls hci_conn_drop(conn)
> without checking whether conn is still valid. When
> hci_le_read_remote_features_sync() blocks waiting for an HCI event,
> another thread can free conn through hci_conn_del(). Fix by adding
> a hci_conn_valid() check before calling hci_conn_drop().
>
> Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
> Signed-off-by: Masahiro Kawada <youjingxiaogao2@gmail.com>
> ---
>  net/bluetooth/hci_conn.c | 6 +++---
>  net/bluetooth/hci_sync.c | 3 +++
>  2 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> index 0795818963a..aa3607327ad 100644
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -1232,15 +1232,15 @@ void hci_conn_del(struct hci_conn *conn)
>   skb_queue_purge(&conn->data_q);
>   skb_queue_purge(&conn->tx_q.queue);
>
> + /* Dequeue callbacks using connection pointer as data */
> + hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
> +
>   /* Remove the connection from the list and cleanup its remaining
>   * state. This is a separate function since for some cases like
>   * BT_CONNECT_SCAN we *only* want the cleanup part without the
>   * rest of hci_conn_del.
>   */
>   hci_conn_cleanup(conn);
> -
> - /* Dequeue callbacks using connection pointer as data */
> - hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
>  }
>
>  struct hci_dev *hci_get_route(bdaddr_t *dst, bdaddr_t *src, uint8_t
> src_type)
> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> index f04a90bce4a..f31086c187f 100644
> --- a/net/bluetooth/hci_sync.c
> +++ b/net/bluetooth/hci_sync.c
> @@ -7371,6 +7371,9 @@ static void le_read_features_complete(struct hci_dev
> *hdev, void *data, int err)
>   if (err == -ECANCELED)
>   return;
>
> + if (!hci_conn_valid(hdev, conn))
> + return;
> +
>   hci_conn_drop(conn);
>  }
>
> -- 
> 2.43.0

Command #2:
I've failed to parse your command.
Did you perhaps forget to provide the branch name, or added an extra ':'?
Please use one of the two supported formats:
1. #syz test
2. #syz test: repo branch-or-commit-hash
Note the lack of ':' in option 1.

Re: #syz test

[kawada]

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#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
master

2026年2月9日(月) 5:03 syzbot <
syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com>:

> > #syz test git://
> git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> > master
> >
> > From d5153b84b90fa80ee0d041d1bd28bd465f7913ec Mon Sep 17 00:00:00 2001
> > From: Masahiro Kawada <youjingxiaogao2@gmail.com>
> > Date: Mon, 9 Feb 2026 04:47:14 +0900
> > Subject: [PATCH] Bluetooth: fix use-after-free in hci_conn_drop
> >
> > Fix a use-after-free in hci_conn_drop triggered via hci_cmd_sync_work.
> >
> > In hci_conn_del(), hci_cmd_sync_dequeue() is called after
> > hci_conn_cleanup() which may have already freed the conn pointer.
> > Fix by moving the dequeue before cleanup.
> >
> > Additionally, le_read_features_complete() calls hci_conn_drop(conn)
> > without checking whether conn is still valid. When
> > hci_le_read_remote_features_sync() blocks waiting for an HCI event,
> > another thread can free conn through hci_conn_del(). Fix by adding
> > a hci_conn_valid() check before calling hci_conn_drop().
> >
> > Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
> > Signed-off-by: Masahiro Kawada <youjingxiaogao2@gmail.com>
> > ---
> >  net/bluetooth/hci_conn.c | 6 +++---
> >  net/bluetooth/hci_sync.c | 3 +++
> >  2 files changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> > index 0795818963a..aa3607327ad 100644
> > --- a/net/bluetooth/hci_conn.c
> > +++ b/net/bluetooth/hci_conn.c
> > @@ -1232,15 +1232,15 @@ void hci_conn_del(struct hci_conn *conn)
> >   skb_queue_purge(&conn->data_q);
> >   skb_queue_purge(&conn->tx_q.queue);
> >
> > + /* Dequeue callbacks using connection pointer as data */
> > + hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
> > +
> >   /* Remove the connection from the list and cleanup its remaining
> >   * state. This is a separate function since for some cases like
> >   * BT_CONNECT_SCAN we *only* want the cleanup part without the
> >   * rest of hci_conn_del.
> >   */
> >   hci_conn_cleanup(conn);
> > -
> > - /* Dequeue callbacks using connection pointer as data */
> > - hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
> >  }
> >
> >  struct hci_dev *hci_get_route(bdaddr_t *dst, bdaddr_t *src, uint8_t
> > src_type)
> > diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> > index f04a90bce4a..f31086c187f 100644
> > --- a/net/bluetooth/hci_sync.c
> > +++ b/net/bluetooth/hci_sync.c
> > @@ -7371,6 +7371,9 @@ static void le_read_features_complete(struct
> hci_dev
> > *hdev, void *data, int err)
> >   if (err == -ECANCELED)
> >   return;
> >
> > + if (!hci_conn_valid(hdev, conn))
> > + return;
> > +
> >   hci_conn_drop(conn);
> >  }
> >
> > --
> > 2.43.0
>
> Command #2:
> I've failed to parse your command.
> Did you perhaps forget to provide the branch name, or added an extra ':'?
> Please use one of the two supported formats:
> 1. #syz test
> 2. #syz test: repo branch-or-commit-hash
> Note the lack of ':' in option 1.
>
>

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[-- Attachment #2: 0001-Bluetooth-fix-use-after-free-in-hci_conn_drop.patch --]
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From d5153b84b90fa80ee0d041d1bd28bd465f7913ec Mon Sep 17 00:00:00 2001
From: Masahiro Kawada <youjingxiaogao2@gmail.com>
Date: Mon, 9 Feb 2026 04:47:14 +0900
Subject: [PATCH] Bluetooth: fix use-after-free in hci_conn_drop

Fix a use-after-free in hci_conn_drop triggered via hci_cmd_sync_work.

In hci_conn_del(), hci_cmd_sync_dequeue() is called after
hci_conn_cleanup() which may have already freed the conn pointer.
Fix by moving the dequeue before cleanup.

Additionally, le_read_features_complete() calls hci_conn_drop(conn)
without checking whether conn is still valid. When
hci_le_read_remote_features_sync() blocks waiting for an HCI event,
another thread can free conn through hci_conn_del(). Fix by adding
a hci_conn_valid() check before calling hci_conn_drop().

Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
Signed-off-by: Masahiro Kawada <youjingxiaogao2@gmail.com>
---
 net/bluetooth/hci_conn.c | 6 +++---
 net/bluetooth/hci_sync.c | 3 +++
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 0795818963a..aa3607327ad 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1232,15 +1232,15 @@ void hci_conn_del(struct hci_conn *conn)
 	skb_queue_purge(&conn->data_q);
 	skb_queue_purge(&conn->tx_q.queue);
 
+	/* Dequeue callbacks using connection pointer as data */
+	hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
+
 	/* Remove the connection from the list and cleanup its remaining
 	 * state. This is a separate function since for some cases like
 	 * BT_CONNECT_SCAN we *only* want the cleanup part without the
 	 * rest of hci_conn_del.
 	 */
 	hci_conn_cleanup(conn);
-
-	/* Dequeue callbacks using connection pointer as data */
-	hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
 }
 
 struct hci_dev *hci_get_route(bdaddr_t *dst, bdaddr_t *src, uint8_t src_type)
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index f04a90bce4a..f31086c187f 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -7371,6 +7371,9 @@ static void le_read_features_complete(struct hci_dev *hdev, void *data, int err)
 	if (err == -ECANCELED)
 		return;
 
+	if (!hci_conn_valid(hdev, conn))
+		return;
+
 	hci_conn_drop(conn);
 }
 
-- 
2.43.0

Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Write in hci_conn_drop (3)

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
Tested-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com

Tested on:

commit:         9845cf73 Add linux-next specific files for 20260205
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10d4eb22580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1679e848890a9e1e
dashboard link: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11b8eb22580000

Note: testing is done by a robot and is best-effort only.

Re: #syz test

[kawada]

[-- Attachment #1.1: Type: text/plain, Size: 3479 bytes --]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
 master

2026年2月9日(月) 5:09 kawada <youjingxiaogao2@gmail.com>:

> #syz test: git://
> git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>
> 2026年2月9日(月) 5:03 syzbot <
> syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com>:
>
>> > #syz test git://
>> git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
>> > master
>> >
>> > From d5153b84b90fa80ee0d041d1bd28bd465f7913ec Mon Sep 17 00:00:00 2001
>> > From: Masahiro Kawada <youjingxiaogao2@gmail.com>
>> > Date: Mon, 9 Feb 2026 04:47:14 +0900
>> > Subject: [PATCH] Bluetooth: fix use-after-free in hci_conn_drop
>> >
>> > Fix a use-after-free in hci_conn_drop triggered via hci_cmd_sync_work.
>> >
>> > In hci_conn_del(), hci_cmd_sync_dequeue() is called after
>> > hci_conn_cleanup() which may have already freed the conn pointer.
>> > Fix by moving the dequeue before cleanup.
>> >
>> > Additionally, le_read_features_complete() calls hci_conn_drop(conn)
>> > without checking whether conn is still valid. When
>> > hci_le_read_remote_features_sync() blocks waiting for an HCI event,
>> > another thread can free conn through hci_conn_del(). Fix by adding
>> > a hci_conn_valid() check before calling hci_conn_drop().
>> >
>> > Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
>> > Closes: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
>> > Signed-off-by: Masahiro Kawada <youjingxiaogao2@gmail.com>
>> > ---
>> >  net/bluetooth/hci_conn.c | 6 +++---
>> >  net/bluetooth/hci_sync.c | 3 +++
>> >  2 files changed, 6 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
>> > index 0795818963a..aa3607327ad 100644
>> > --- a/net/bluetooth/hci_conn.c
>> > +++ b/net/bluetooth/hci_conn.c
>> > @@ -1232,15 +1232,15 @@ void hci_conn_del(struct hci_conn *conn)
>> >   skb_queue_purge(&conn->data_q);
>> >   skb_queue_purge(&conn->tx_q.queue);
>> >
>> > + /* Dequeue callbacks using connection pointer as data */
>> > + hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
>> > +
>> >   /* Remove the connection from the list and cleanup its remaining
>> >   * state. This is a separate function since for some cases like
>> >   * BT_CONNECT_SCAN we *only* want the cleanup part without the
>> >   * rest of hci_conn_del.
>> >   */
>> >   hci_conn_cleanup(conn);
>> > -
>> > - /* Dequeue callbacks using connection pointer as data */
>> > - hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
>> >  }
>> >
>> >  struct hci_dev *hci_get_route(bdaddr_t *dst, bdaddr_t *src, uint8_t
>> > src_type)
>> > diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
>> > index f04a90bce4a..f31086c187f 100644
>> > --- a/net/bluetooth/hci_sync.c
>> > +++ b/net/bluetooth/hci_sync.c
>> > @@ -7371,6 +7371,9 @@ static void le_read_features_complete(struct
>> hci_dev
>> > *hdev, void *data, int err)
>> >   if (err == -ECANCELED)
>> >   return;
>> >
>> > + if (!hci_conn_valid(hdev, conn))
>> > + return;
>> > +
>> >   hci_conn_drop(conn);
>> >  }
>> >
>> > --
>> > 2.43.0
>>
>> Command #2:
>> I've failed to parse your command.
>> Did you perhaps forget to provide the branch name, or added an extra ':'?
>> Please use one of the two supported formats:
>> 1. #syz test
>> 2. #syz test: repo branch-or-commit-hash
>> Note the lack of ':' in option 1.
>>
>>

[-- Attachment #1.2: Type: text/html, Size: 5078 bytes --]

[-- Attachment #2: 0001-Bluetooth-fix-use-after-free-in-hci_conn_drop.patch --]
[-- Type: application/octet-stream, Size: 2579 bytes --]

From d5153b84b90fa80ee0d041d1bd28bd465f7913ec Mon Sep 17 00:00:00 2001
From: Masahiro Kawada <youjingxiaogao2@gmail.com>
Date: Mon, 9 Feb 2026 04:47:14 +0900
Subject: [PATCH] Bluetooth: fix use-after-free in hci_conn_drop

Fix a use-after-free in hci_conn_drop triggered via hci_cmd_sync_work.

In hci_conn_del(), hci_cmd_sync_dequeue() is called after
hci_conn_cleanup() which may have already freed the conn pointer.
Fix by moving the dequeue before cleanup.

Additionally, le_read_features_complete() calls hci_conn_drop(conn)
without checking whether conn is still valid. When
hci_le_read_remote_features_sync() blocks waiting for an HCI event,
another thread can free conn through hci_conn_del(). Fix by adding
a hci_conn_valid() check before calling hci_conn_drop().

Fixes: 881559af5f5c ("Bluetooth: hci_sync: Attempt to dequeue connection attempt")
Fixes: a106e50be74b ("Bluetooth: HCI: Add support for LL Extended Feature Set")
Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
Tested-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
Signed-off-by: Masahiro Kawada <youjingxiaogao2@gmail.com>
---
 net/bluetooth/hci_conn.c | 6 +++---
 net/bluetooth/hci_sync.c | 3 +++
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 0795818963a..aa3607327ad 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1232,15 +1232,15 @@ void hci_conn_del(struct hci_conn *conn)
 	skb_queue_purge(&conn->data_q);
 	skb_queue_purge(&conn->tx_q.queue);
 
+	/* Dequeue callbacks using connection pointer as data */
+	hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
+
 	/* Remove the connection from the list and cleanup its remaining
 	 * state. This is a separate function since for some cases like
 	 * BT_CONNECT_SCAN we *only* want the cleanup part without the
 	 * rest of hci_conn_del.
 	 */
 	hci_conn_cleanup(conn);
-
-	/* Dequeue callbacks using connection pointer as data */
-	hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);
 }
 
 struct hci_dev *hci_get_route(bdaddr_t *dst, bdaddr_t *src, uint8_t src_type)
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index f04a90bce4a..f31086c187f 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -7371,6 +7371,9 @@ static void le_read_features_complete(struct hci_dev *hdev, void *data, int err)
 	if (err == -ECANCELED)
 		return;
 
+	if (!hci_conn_valid(hdev, conn))
+		return;
+
 	hci_conn_drop(conn);
 }
 
-- 
2.43.0

Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Write in hci_conn_drop (3)

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
Tested-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com

Tested on:

commit:         9845cf73 Add linux-next specific files for 20260205
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=177cc2e6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1679e848890a9e1e
dashboard link: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=106124aa580000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Write in hci_conn_drop (3)

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to apply patch:
checking file net/bluetooth/hci_conn.c
Hunk #1 succeeded at 1232 with fuzz 1.
checking file net/bluetooth/hci_sync.c
patch: **** unexpected end of file in patch



Tested on:

commit:         9845cf73 Add linux-next specific files for 20260205
git tree:       linux-next
kernel config:  https://syzkaller.appspot.com/x/.config?x=6336d8e94a7c517d
dashboard link: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
compiler:       
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1038eb22580000

[syzbot] [bluetooth?] KASAN: slab-use-after-free Write in hci_conn_drop (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    7d31f578f323 Add linux-next specific files for 20251128
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1715f484580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6336d8e94a7c517d
dashboard link: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14d34112580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13f0e112580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6b49d8ad90de/disk-7d31f578.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/dbe2d4988ca7/vmlinux-7d31f578.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fc0448ab2411/bzImage-7d31f578.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1383 [inline]
BUG: KASAN: slab-use-after-free in hci_conn_drop+0x34/0x2b0 include/net/bluetooth/hci_core.h:1688
Write of size 4 at addr ffff88807b2a0010 by task kworker/u9:1/5148

CPU: 0 UID: 0 PID: 5148 Comm: kworker/u9:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:200
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1383 [inline]
 hci_conn_drop+0x34/0x2b0 include/net/bluetooth/hci_core.h:1688
 hci_cmd_sync_work+0x262/0x400 net/bluetooth/hci_sync.c:334
 process_one_work+0x93a/0x15a0 kernel/workqueue.c:3261
 process_scheduled_works kernel/workqueue.c:3344 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3425
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>

Allocated by task 5848:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:397 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:414
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __kmalloc_cache_noprof+0x3e2/0x700 mm/slub.c:5771
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 __hci_conn_add+0x3c5/0x1b30 net/bluetooth/hci_conn.c:963
 le_conn_complete_evt+0x6f6/0x1420 net/bluetooth/hci_event.c:5714
 hci_le_enh_conn_complete_evt+0x189/0x4a0 net/bluetooth/hci_event.c:5861
 hci_event_func net/bluetooth/hci_event.c:7716 [inline]
 hci_event_packet+0x78f/0x1260 net/bluetooth/hci_event.c:7773
 hci_rx_work+0x3ee/0x1060 net/bluetooth/hci_core.c:4076
 process_one_work+0x93a/0x15a0 kernel/workqueue.c:3261
 process_scheduled_works kernel/workqueue.c:3344 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3425
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Freed by task 5848:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6663 [inline]
 kfree+0x1c0/0x660 mm/slub.c:6871
 device_release+0x9e/0x1d0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x228/0x570 lib/kobject.c:737
 hci_conn_cleanup net/bluetooth/hci_conn.c:173 [inline]
 hci_conn_del+0xc36/0x1240 net/bluetooth/hci_conn.c:1234
 hci_disconn_complete_evt+0x64e/0x950 net/bluetooth/hci_event.c:3451
 hci_event_func net/bluetooth/hci_event.c:7719 [inline]
 hci_event_packet+0x7e3/0x1260 net/bluetooth/hci_event.c:7773
 hci_rx_work+0x3ee/0x1060 net/bluetooth/hci_core.c:4076
 process_one_work+0x93a/0x15a0 kernel/workqueue.c:3261
 process_scheduled_works kernel/workqueue.c:3344 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3425
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

The buggy address belongs to the object at ffff88807b2a0000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 16 bytes inside of
 freed 8192-byte region [ffff88807b2a0000, ffff88807b2a2000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b2a0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813fe27280 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe27280 dead000000000122 0000000000000000
head: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0001eca801 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5848, tgid 5848 (kworker/u9:2), ts 108134257211, free_ts 108012219828
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1846
 prep_new_page mm/page_alloc.c:1854 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3915
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab+0x86/0x3b0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xf2b/0x1960 mm/slub.c:4651
 __slab_alloc+0x65/0x100 mm/slub.c:4774
 __slab_alloc_node mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:5246 [inline]
 __kmalloc_cache_noprof+0x41e/0x700 mm/slub.c:5766
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 __hci_conn_add+0x3c5/0x1b30 net/bluetooth/hci_conn.c:963
 le_conn_complete_evt+0x6f6/0x1420 net/bluetooth/hci_event.c:5714
 hci_le_enh_conn_complete_evt+0x189/0x4a0 net/bluetooth/hci_event.c:5861
 hci_event_func net/bluetooth/hci_event.c:7716 [inline]
 hci_event_packet+0x78f/0x1260 net/bluetooth/hci_event.c:7773
 hci_rx_work+0x3ee/0x1060 net/bluetooth/hci_core.c:4076
 process_one_work+0x93a/0x15a0 kernel/workqueue.c:3261
 process_scheduled_works kernel/workqueue.c:3344 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3425
 kthread+0x711/0x8a0 kernel/kthread.c:463
page last free pid 5999 tgid 5999 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0xbc8/0xd30 mm/page_alloc.c:2943
 discard_slab mm/slub.c:3346 [inline]
 __put_partials+0x146/0x170 mm/slub.c:3886
 put_cpu_partial+0x1f2/0x2d0 mm/slub.c:3961
 __slab_free+0x288/0x2a0 mm/slub.c:5947
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:349
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4948 [inline]
 slab_alloc_node mm/slub.c:5258 [inline]
 kmem_cache_alloc_noprof+0x37d/0x710 mm/slub.c:5265
 getname_flags+0xb8/0x540 fs/namei.c:146
 getname include/linux/fs.h:2498 [inline]
 do_sys_openat2+0xbc/0x200 fs/open.c:1426
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1447
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88807b29ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807b29ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807b2a0000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88807b2a0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807b2a0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

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If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Write in hci_conn_drop (3)

[Edward Adam Davis]

#syz test

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index a9f5b1a68356..cbbb1ad3e78a 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -329,9 +329,11 @@ static void hci_cmd_sync_work(struct work_struct *work)
 			int err;
 
 			hci_req_sync_lock(hdev);
+			hci_dev_lock(hdev);
 			err = entry->func(hdev, entry->data);
 			if (entry->destroy)
 				entry->destroy(hdev, entry->data, err);
+			hci_dev_unlock(hdev);
 			hci_req_sync_unlock(hdev);
 		}
 

Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Write in hci_conn_drop (3)

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com
Tested-by: syzbot+3609b9b48e68e1fe47fd@syzkaller.appspotmail.com

Tested on:

commit:         b2c27842 Add linux-next specific files for 20251203
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=141f801a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=caadf525b0ab8d17
dashboard link: https://syzkaller.appspot.com/bug?extid=3609b9b48e68e1fe47fd
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1391d4c2580000

Note: testing is done by a robot and is best-effort only.