[syzbot] [trace?] WARNING in ring_buffer_map_get_reader (3)

[syzbot] [trace?] WARNING in ring_buffer_map_get_reader (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    89a312991dc6 Merge tag 'cifs-fixes-7.3-rc2' of https://git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12e4bc15580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5c3949d762a91f
dashboard link: https://syzkaller.appspot.com/bug?extid=de3d7f9bcc9212f3fae1
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-89a31299.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2299fb3a049a/vmlinux-89a31299.xz
kernel image: https://storage.googleapis.com/syzbot-assets/556be545d7b6/bzImage-89a31299.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+de3d7f9bcc9212f3fae1@syzkaller.appspotmail.com

Cannot find set identified by id 0 to match
------------[ cut here ]------------
!reader
WARNING: kernel/trace/ring_buffer.c:7927 at ring_buffer_map_get_reader+0x5f3/0x930 kernel/trace/ring_buffer.c:7927, CPU#0: syz.2.1764/13608
Modules linked in:
CPU: 0 UID: 0 PID: 13608 Comm: syz.2.1764 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:ring_buffer_map_get_reader+0x5f3/0x930 kernel/trace/ring_buffer.c:7927
Code: ff 48 89 df e8 2e 21 fe ff 48 89 c5 e8 46 8b fb ff 48 85 ed 0f 85 9f fc ff ff 4c 8b 74 24 58 4c 8b 7c 24 60 e8 2e 8b fb ff 90 <0f> 0b 90 e8 25 8b fb ff 49 8d bf d0 01 00 00 48 b8 00 00 00 00 00
RSP: 0018:ffffc90006b57d98 EFLAGS: 00010087
RAX: 000000000000086c RBX: ffff88801c0e5000 RCX: ffffc90024800000
RDX: 0000000000080000 RSI: ffffffff821064e2 RDI: ffff888027852580
RBP: 0000000000000000 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: ffff88801c0e50b0 R12: ffff88801c0e50b8
R13: dffffc0000000000 R14: ffff88801c0e5198 R15: ffff88801c0ab800
FS:  00007fa41bfdb6c0(0000) GS:ffff8880d5b61000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f60453c8ff8 CR3: 0000000035d0b000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 tracing_buffers_ioctl+0x2e6/0x3d0 kernel/trace/trace.c:7392
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa41b19e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa41bfdb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa41b425fa0 RCX: 00007fa41b19e159
RDX: 0000000000000000 RSI: 0000000000005220 RDI: 0000000000000007
RBP: 00007fa41b235024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa41b426038 R14: 00007fa41b425fa0 R15: 00007ffd22388a08
 </TASK>


---
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Re: [syzbot] [trace?] WARNING in ring_buffer_map_get_reader (3)

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    df2908090cda Linux 7.3-rc2
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1216caf9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5c3949d762a91f
dashboard link: https://syzkaller.appspot.com/bug?extid=de3d7f9bcc9212f3fae1
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1616caf9580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+de3d7f9bcc9212f3fae1@syzkaller.appspotmail.com

Ring buffer [0] commit overrun lost 3 events at timestamp:71798603963
------------[ cut here ]------------
!reader
WARNING: kernel/trace/ring_buffer.c:7998 at ring_buffer_map_get_reader+0x5f3/0x930 kernel/trace/ring_buffer.c:7998, CPU#1: syz-executor388/6024
Modules linked in:
CPU: 1 UID: 0 PID: 6024 Comm: syz-executor388 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:ring_buffer_map_get_reader+0x5f3/0x930 kernel/trace/ring_buffer.c:7998
Code: ff 48 89 df e8 be 22 fe ff 48 89 c5 e8 a6 88 fb ff 48 85 ed 0f 85 9f fc ff ff 4c 8b 74 24 58 4c 8b 7c 24 60 e8 8e 88 fb ff 90 <0f> 0b 90 e8 85 88 fb ff 49 8d bf d0 01 00 00 48 b8 00 00 00 00 00
RSP: 0018:ffffc90003977d98 EFLAGS: 00010093
RAX: 0000000000000000 RBX: ffff88801c0e5000 RCX: 0000000000000001
RDX: ffff8880333d4b00 RSI: ffffffff82108882 RDI: ffff8880333d4b00
RBP: 0000000000000000 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: ffff88801c0e50b0 R12: ffff88801c0e50b8
R13: dffffc0000000000 R14: ffff88801c0e5198 R15: ffff88801c0ab800
FS:  00007f337024b6c0(0000) GS:ffff8880d5c5d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000559c2c45caa0 CR3: 000000003dec3000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 tracing_buffers_ioctl+0x2e6/0x3d0 kernel/trace/trace.c:7381
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3370a8136b
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007f337024b130 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f337024bcdc RCX: 00007f3370a8136b
RDX: 0000000000000000 RSI: 0000000000005220 RDI: 0000000000000004
RBP: 0000000000000021 R08: 0000000000000000 R09: 00007f337024b6c0
R10: 0000000000000008 R11: 0000000000000246 R12: ffffffffffffffd0
R13: 0000000000000000 R14: 00007ffc1cde9710 R15: 00007ffc1cde97f8
 </TASK>


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

Forwarded: Re: test patch

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Subject: Re: test patch
Author: tahasami8@gmail.com

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

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9c03a555a6ba..98130182e05d 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -7995,8 +7995,10 @@ int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu)
 		goto out;
 
 	reader = rb_get_reader_page(cpu_buffer);
-	if (WARN_ON(!reader))
+	if (!reader) {
+		WARN_ON(cpu_buffer->reader_page != cpu_buffer->commit_page);
 		goto out;
+	}
 
 	/* Check if any events were dropped */
 	missed_events = cpu_buffer->lost_events;

Forwarded: Re: test patch

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Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

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

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index cdd1dfc666c4..9da860589861 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -603,6 +603,41 @@ static int gserial_wakeup_host(struct gserial *gser)
 
 /* TTY Driver */
 
+static int gs_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct gs_port *port;
+	struct tty_port *tport;
+	int ret;
+
+	mutex_lock(&ports[tty->index].lock);
+	port = ports[tty->index].port;
+	if (!port) {
+		mutex_unlock(&ports[tty->index].lock);
+		return -ENODEV;
+	}
+
+	tport = tty_port_get(&port->port);
+	mutex_unlock(&ports[tty->index].lock);
+
+	if (!tport)
+		return -ENODEV;
+
+	ret = tty_port_install(tport, driver, tty);
+	if (ret) {
+		tty_port_put(tport);
+		return ret;
+	}
+
+	tty->driver_data = port;
+
+	return 0;
+}
+
+static void gs_cleanup(struct tty_struct *tty)
+{
+	tty_port_put(tty->port);
+}
+
 /*
  * gs_open sets up the link between a gs_port and its associated TTY.
  * That link is broken *only* by TTY close(), and all driver methods
@@ -615,7 +650,7 @@ static int gs_open(struct tty_struct *tty, struct file *file)
 	int		status = 0;
 
 	mutex_lock(&ports[port_num].lock);
-	port = ports[port_num].port;
+	port = tty->driver_data;
 	if (!port) {
 		status = -ENODEV;
 		goto out;
@@ -648,7 +683,6 @@ static int gs_open(struct tty_struct *tty, struct file *file)
 	if (port->port.count++)
 		goto exit_unlock_port;
 
-	tty->driver_data = port;
 	port->port.tty = tty;
 
 	/* if connected, start the I/O stream */
@@ -695,14 +729,16 @@ static void gs_close(struct tty_struct *tty, struct file *file)
 	struct gs_port *port = tty->driver_data;
 	struct gserial	*gser;
 
+	if (!port)
+		return;
+
 	spin_lock_irq(&port->port_lock);
 
 	if (port->port.count != 1) {
 raced_with_open:
-		if (port->port.count == 0)
-			WARN_ON(1);
-		else
+		if (port->port.count > 0)
 			--port->port.count;
+
 		goto exit;
 	}
 
@@ -911,6 +947,8 @@ static int gs_get_icount(struct tty_struct *tty,
 static const struct tty_operations gs_tty_ops = {
 	.open =			gs_open,
 	.close =		gs_close,
+	.install =		gs_install,
+	.cleanup =		gs_cleanup,
 	.write =		gs_write,
 	.put_char =		gs_put_char,
 	.flush_chars =		gs_flush_chars,
@@ -1203,6 +1241,18 @@ static void gs_console_exit(struct gs_port *port)
 
 #endif
 
+static void gs_port_destruct(struct tty_port *tport)
+{
+	struct gs_port *port = container_of(tport, struct gs_port, port);
+
+	kfree(port);
+}
+
+static const struct tty_port_operations gs_port_ops = {
+	.destruct = gs_port_destruct,
+};
+
+
 static int
 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 {
@@ -1222,6 +1272,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 	}
 
 	tty_port_init(&port->port);
+	port->port.ops = &gs_port_ops;
 	spin_lock_init(&port->port_lock);
 	init_waitqueue_head(&port->drain_wait);
 	init_waitqueue_head(&port->close_wait);
@@ -1258,8 +1309,7 @@ static void gserial_free_port(struct gs_port *port)
 	/* wait for old opens to finish */
 	wait_event(port->close_wait, gs_closed(port));
 	WARN_ON(port->port_usb != NULL);
-	tty_port_destroy(&port->port);
-	kfree(port);
+	tty_port_put(&port->port);
 }
 
 void gserial_free_line(unsigned char port_num)

Forwarded: Re: test patch

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linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

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

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index cdd1dfc666c4..5974a9303ecf 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -603,6 +603,41 @@ static int gserial_wakeup_host(struct gserial *gser)
 
 /* TTY Driver */
 
+static int gs_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct gs_port *port;
+	struct tty_port *tport;
+	int ret;
+
+	mutex_lock(&ports[tty->index].lock);
+	port = ports[tty->index].port;
+	if (!port) {
+		mutex_unlock(&ports[tty->index].lock);
+		return -ENODEV;
+	}
+
+	tport = tty_port_get(&port->port);
+	mutex_unlock(&ports[tty->index].lock);
+
+	if (!tport)
+		return -ENODEV;
+
+	ret = tty_port_install(tport, driver, tty);
+	if (ret) {
+		tty_port_put(tport);
+		return ret;
+	}
+
+	tty->driver_data = port;
+
+	return 0;
+}
+
+static void gs_cleanup(struct tty_struct *tty)
+{
+	tty_port_put(tty->port);
+}
+
 /*
  * gs_open sets up the link between a gs_port and its associated TTY.
  * That link is broken *only* by TTY close(), and all driver methods
@@ -695,14 +730,16 @@ static void gs_close(struct tty_struct *tty, struct file *file)
 	struct gs_port *port = tty->driver_data;
 	struct gserial	*gser;
 
+	if (!port)
+		return;
+
 	spin_lock_irq(&port->port_lock);
 
 	if (port->port.count != 1) {
 raced_with_open:
-		if (port->port.count == 0)
-			WARN_ON(1);
-		else
+		if (port->port.count > 0)
 			--port->port.count;
+
 		goto exit;
 	}
 
@@ -911,6 +948,8 @@ static int gs_get_icount(struct tty_struct *tty,
 static const struct tty_operations gs_tty_ops = {
 	.open =			gs_open,
 	.close =		gs_close,
+	.install =		gs_install,
+	.cleanup =		gs_cleanup,
 	.write =		gs_write,
 	.put_char =		gs_put_char,
 	.flush_chars =		gs_flush_chars,
@@ -1203,6 +1242,18 @@ static void gs_console_exit(struct gs_port *port)
 
 #endif
 
+static void gs_port_destruct(struct tty_port *tport)
+{
+	struct gs_port *port = container_of(tport, struct gs_port, port);
+
+	kfree(port);
+}
+
+static const struct tty_port_operations gs_port_ops = {
+	.destruct = gs_port_destruct,
+};
+
+
 static int
 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 {
@@ -1222,6 +1273,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 	}
 
 	tty_port_init(&port->port);
+	port->port.ops = &gs_port_ops;
 	spin_lock_init(&port->port_lock);
 	init_waitqueue_head(&port->drain_wait);
 	init_waitqueue_head(&port->close_wait);
@@ -1258,8 +1310,7 @@ static void gserial_free_port(struct gs_port *port)
 	/* wait for old opens to finish */
 	wait_event(port->close_wait, gs_closed(port));
 	WARN_ON(port->port_usb != NULL);
-	tty_port_destroy(&port->port);
-	kfree(port);
+	tty_port_put(&port->port);
 }
 
 void gserial_free_line(unsigned char port_num)

Forwarded: Re: test patch

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linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

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Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

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

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index cdd1dfc666c4..5974a9303ecf 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -603,6 +603,41 @@ static int gserial_wakeup_host(struct gserial *gser)
 
 /* TTY Driver */
 
+static int gs_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct gs_port *port;
+	struct tty_port *tport;
+	int ret;
+
+	mutex_lock(&ports[tty->index].lock);
+	port = ports[tty->index].port;
+	if (!port) {
+		mutex_unlock(&ports[tty->index].lock);
+		return -ENODEV;
+	}
+
+	tport = tty_port_get(&port->port);
+	mutex_unlock(&ports[tty->index].lock);
+
+	if (!tport)
+		return -ENODEV;
+
+	ret = tty_port_install(tport, driver, tty);
+	if (ret) {
+		tty_port_put(tport);
+		return ret;
+	}
+
+	tty->driver_data = port;
+
+	return 0;
+}
+
+static void gs_cleanup(struct tty_struct *tty)
+{
+	tty_port_put(tty->port);
+}
+
 /*
  * gs_open sets up the link between a gs_port and its associated TTY.
  * That link is broken *only* by TTY close(), and all driver methods
@@ -695,14 +730,16 @@ static void gs_close(struct tty_struct *tty, struct file *file)
 	struct gs_port *port = tty->driver_data;
 	struct gserial	*gser;
 
+	if (!port)
+		return;
+
 	spin_lock_irq(&port->port_lock);
 
 	if (port->port.count != 1) {
 raced_with_open:
-		if (port->port.count == 0)
-			WARN_ON(1);
-		else
+		if (port->port.count > 0)
 			--port->port.count;
+
 		goto exit;
 	}
 
@@ -911,6 +948,8 @@ static int gs_get_icount(struct tty_struct *tty,
 static const struct tty_operations gs_tty_ops = {
 	.open =			gs_open,
 	.close =		gs_close,
+	.install =		gs_install,
+	.cleanup =		gs_cleanup,
 	.write =		gs_write,
 	.put_char =		gs_put_char,
 	.flush_chars =		gs_flush_chars,
@@ -1203,6 +1242,18 @@ static void gs_console_exit(struct gs_port *port)
 
 #endif
 
+static void gs_port_destruct(struct tty_port *tport)
+{
+	struct gs_port *port = container_of(tport, struct gs_port, port);
+
+	kfree(port);
+}
+
+static const struct tty_port_operations gs_port_ops = {
+	.destruct = gs_port_destruct,
+};
+
+
 static int
 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 {
@@ -1222,6 +1273,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 	}
 
 	tty_port_init(&port->port);
+	port->port.ops = &gs_port_ops;
 	spin_lock_init(&port->port_lock);
 	init_waitqueue_head(&port->drain_wait);
 	init_waitqueue_head(&port->close_wait);
@@ -1258,8 +1310,7 @@ static void gserial_free_port(struct gs_port *port)
 	/* wait for old opens to finish */
 	wait_event(port->close_wait, gs_closed(port));
 	WARN_ON(port->port_usb != NULL);
-	tty_port_destroy(&port->port);
-	kfree(port);
+	tty_port_put(&port->port);
 }
 
 void gserial_free_line(unsigned char port_num)

Forwarded: Re: test patch

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Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

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

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index cdd1dfc666c4..c2fba561ba03 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -603,6 +603,41 @@ static int gserial_wakeup_host(struct gserial *gser)
 
 /* TTY Driver */
 
+static int gs_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct gs_port *port;
+	struct tty_port *tport;
+	int ret;
+
+	mutex_lock(&ports[tty->index].lock);
+	port = ports[tty->index].port;
+	if (!port) {
+		mutex_unlock(&ports[tty->index].lock);
+		return -ENODEV;
+	}
+
+	tport = tty_port_get(&port->port);
+	mutex_unlock(&ports[tty->index].lock);
+
+	if (!tport)
+		return -ENODEV;
+
+	ret = tty_port_install(tport, driver, tty);
+	if (ret) {
+		tty_port_put(tport);
+		return ret;
+	}
+
+	tty->driver_data = port;
+
+	return 0;
+}
+
+static void gs_cleanup(struct tty_struct *tty)
+{
+	tty_port_put(tty->port);
+}
+
 /*
  * gs_open sets up the link between a gs_port and its associated TTY.
  * That link is broken *only* by TTY close(), and all driver methods
@@ -695,15 +730,17 @@ static void gs_close(struct tty_struct *tty, struct file *file)
 	struct gs_port *port = tty->driver_data;
 	struct gserial	*gser;
 
+	if (!port)
+		return;
+
 	spin_lock_irq(&port->port_lock);
 
 	if (port->port.count != 1) {
 raced_with_open:
-		if (port->port.count == 0)
-			WARN_ON(1);
-		else
+		if (port->port.count > 0)
 			--port->port.count;
-		goto exit;
+
+		goto exit
 	}
 
 	pr_debug("gs_close: ttyGS%d (%p,%p) ...\n", port->port_num, tty, file);
@@ -911,6 +948,8 @@ static int gs_get_icount(struct tty_struct *tty,
 static const struct tty_operations gs_tty_ops = {
 	.open =			gs_open,
 	.close =		gs_close,
+	.install =		gs_install,
+	.cleanup =		gs_cleanup,
 	.write =		gs_write,
 	.put_char =		gs_put_char,
 	.flush_chars =		gs_flush_chars,
@@ -1203,6 +1242,18 @@ static void gs_console_exit(struct gs_port *port)
 
 #endif
 
+static void gs_port_destruct(struct tty_port *tport)
+{
+	struct gs_port *port = container_of(tport, struct gs_port, port);
+
+	kfree(port);
+}
+
+static const struct tty_port_operations gs_port_ops = {
+	.destruct = gs_port_destruct,
+};
+
+
 static int
 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 {
@@ -1222,6 +1273,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 	}
 
 	tty_port_init(&port->port);
+	port->port.ops = &gs_port_ops;
 	spin_lock_init(&port->port_lock);
 	init_waitqueue_head(&port->drain_wait);
 	init_waitqueue_head(&port->close_wait);
@@ -1258,8 +1310,7 @@ static void gserial_free_port(struct gs_port *port)
 	/* wait for old opens to finish */
 	wait_event(port->close_wait, gs_closed(port));
 	WARN_ON(port->port_usb != NULL);
-	tty_port_destroy(&port->port);
-	kfree(port);
+	tty_port_put(&port->port);
 }
 
 void gserial_free_line(unsigned char port_num)

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Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

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

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index cdd1dfc666c4..4020807a4d2c 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -603,6 +603,41 @@ static int gserial_wakeup_host(struct gserial *gser)
 
 /* TTY Driver */
 
+static int gs_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct gs_port *port;
+	struct tty_port *tport;
+	int ret;
+
+	mutex_lock(&ports[tty->index].lock);
+	port = ports[tty->index].port;
+	if (!port) {
+		mutex_unlock(&ports[tty->index].lock);
+		return -ENODEV;
+	}
+
+	tport = tty_port_get(&port->port);
+	mutex_unlock(&ports[tty->index].lock);
+
+	if (!tport)
+		return -ENODEV;
+
+	ret = tty_port_install(tport, driver, tty);
+	if (ret) {
+		tty_port_put(tport);
+		return ret;
+	}
+
+	tty->driver_data = port;
+
+	return 0;
+}
+
+static void gs_cleanup(struct tty_struct *tty)
+{
+	tty_port_put(tty->port);
+}
+
 /*
  * gs_open sets up the link between a gs_port and its associated TTY.
  * That link is broken *only* by TTY close(), and all driver methods
@@ -695,6 +730,9 @@ static void gs_close(struct tty_struct *tty, struct file *file)
 	struct gs_port *port = tty->driver_data;
 	struct gserial	*gser;
 
+	if (!port)
+		return;
+
 	spin_lock_irq(&port->port_lock);
 
 	if (port->port.count != 1) {
@@ -911,6 +949,8 @@ static int gs_get_icount(struct tty_struct *tty,
 static const struct tty_operations gs_tty_ops = {
 	.open =			gs_open,
 	.close =		gs_close,
+	.install =		gs_install,
+	.cleanup =		gs_cleanup,
 	.write =		gs_write,
 	.put_char =		gs_put_char,
 	.flush_chars =		gs_flush_chars,
@@ -1203,6 +1243,18 @@ static void gs_console_exit(struct gs_port *port)
 
 #endif
 
+static void gs_port_destruct(struct tty_port *tport)
+{
+	struct gs_port *port = container_of(tport, struct gs_port, port);
+
+	kfree(port);
+}
+
+static const struct tty_port_operations gs_port_ops = {
+	.destruct = gs_port_destruct,
+};
+
+
 static int
 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 {
@@ -1222,6 +1274,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 	}
 
 	tty_port_init(&port->port);
+	port->port.ops = &gs_port_ops;
 	spin_lock_init(&port->port_lock);
 	init_waitqueue_head(&port->drain_wait);
 	init_waitqueue_head(&port->close_wait);
@@ -1258,8 +1311,7 @@ static void gserial_free_port(struct gs_port *port)
 	/* wait for old opens to finish */
 	wait_event(port->close_wait, gs_closed(port));
 	WARN_ON(port->port_usb != NULL);
-	tty_port_destroy(&port->port);
-	kfree(port);
+	tty_port_put(&port->port);
 }
 
 void gserial_free_line(unsigned char port_num)

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Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

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

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index cdd1dfc666c4..4435cc42d1c0 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -603,6 +603,41 @@ static int gserial_wakeup_host(struct gserial *gser)
 
 /* TTY Driver */
 
+static int gs_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct gs_port *port;
+	struct tty_port *tport;
+	int ret;
+
+	mutex_lock(&ports[tty->index].lock);
+	port = ports[tty->index].port;
+	if (!port) {
+		mutex_unlock(&ports[tty->index].lock);
+		return -ENODEV;
+	}
+
+	tport = tty_port_get(&port->port);
+	mutex_unlock(&ports[tty->index].lock);
+
+	if (!tport)
+		return -ENODEV;
+
+	ret = tty_port_install(tport, driver, tty);
+	if (ret) {
+		tty_port_put(tport);
+		return ret;
+	}
+
+	tty->driver_data = port;
+
+	return 0;
+}
+
+static void gs_cleanup(struct tty_struct *tty)
+{
+	tty_port_put(tty->port);
+}
+
 /*
  * gs_open sets up the link between a gs_port and its associated TTY.
  * That link is broken *only* by TTY close(), and all driver methods
@@ -911,6 +946,8 @@ static int gs_get_icount(struct tty_struct *tty,
 static const struct tty_operations gs_tty_ops = {
 	.open =			gs_open,
 	.close =		gs_close,
+	.install =		gs_install,
+	.cleanup =		gs_cleanup,
 	.write =		gs_write,
 	.put_char =		gs_put_char,
 	.flush_chars =		gs_flush_chars,
@@ -1203,6 +1240,18 @@ static void gs_console_exit(struct gs_port *port)
 
 #endif
 
+static void gs_port_destruct(struct tty_port *tport)
+{
+	struct gs_port *port = container_of(tport, struct gs_port, port);
+
+	kfree(port);
+}
+
+static const struct tty_port_operations gs_port_ops = {
+	.destruct = gs_port_destruct,
+};
+
+
 static int
 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 {
@@ -1222,6 +1271,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 	}
 
 	tty_port_init(&port->port);
+	port->port.ops = &gs_port_ops;
 	spin_lock_init(&port->port_lock);
 	init_waitqueue_head(&port->drain_wait);
 	init_waitqueue_head(&port->close_wait);
@@ -1258,8 +1308,7 @@ static void gserial_free_port(struct gs_port *port)
 	/* wait for old opens to finish */
 	wait_event(port->close_wait, gs_closed(port));
 	WARN_ON(port->port_usb != NULL);
-	tty_port_destroy(&port->port);
-	kfree(port);
+	tty_port_put(&port->port);
 }
 
 void gserial_free_line(unsigned char port_num)

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Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

#syz test

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index cdd1dfc666c4..4435cc42d1c0 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -603,6 +603,41 @@ static int gserial_wakeup_host(struct gserial *gser)
 
 /* TTY Driver */
 
+static int gs_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct gs_port *port;
+	struct tty_port *tport;
+	int ret;
+
+	mutex_lock(&ports[tty->index].lock);
+	port = ports[tty->index].port;
+	if (!port) {
+		mutex_unlock(&ports[tty->index].lock);
+		return -ENODEV;
+	}
+
+	tport = tty_port_get(&port->port);
+	mutex_unlock(&ports[tty->index].lock);
+
+	if (!tport)
+		return -ENODEV;
+
+	ret = tty_port_install(tport, driver, tty);
+	if (ret) {
+		tty_port_put(tport);
+		return ret;
+	}
+
+	tty->driver_data = port;
+
+	return 0;
+}
+
+static void gs_cleanup(struct tty_struct *tty)
+{
+	tty_port_put(tty->port);
+}
+
 /*
  * gs_open sets up the link between a gs_port and its associated TTY.
  * That link is broken *only* by TTY close(), and all driver methods
@@ -911,6 +946,8 @@ static int gs_get_icount(struct tty_struct *tty,
 static const struct tty_operations gs_tty_ops = {
 	.open =			gs_open,
 	.close =		gs_close,
+	.install =		gs_install,
+	.cleanup =		gs_cleanup,
 	.write =		gs_write,
 	.put_char =		gs_put_char,
 	.flush_chars =		gs_flush_chars,
@@ -1203,6 +1240,18 @@ static void gs_console_exit(struct gs_port *port)
 
 #endif
 
+static void gs_port_destruct(struct tty_port *tport)
+{
+	struct gs_port *port = container_of(tport, struct gs_port, port);
+
+	kfree(port);
+}
+
+static const struct tty_port_operations gs_port_ops = {
+	.destruct = gs_port_destruct,
+};
+
+
 static int
 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 {
@@ -1222,6 +1271,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 	}
 
 	tty_port_init(&port->port);
+	port->port.ops = &gs_port_ops;
 	spin_lock_init(&port->port_lock);
 	init_waitqueue_head(&port->drain_wait);
 	init_waitqueue_head(&port->close_wait);
@@ -1258,8 +1308,7 @@ static void gserial_free_port(struct gs_port *port)
 	/* wait for old opens to finish */
 	wait_event(port->close_wait, gs_closed(port));
 	WARN_ON(port->port_usb != NULL);
-	tty_port_destroy(&port->port);
-	kfree(port);
+	tty_port_put(&port->port);
 }
 
 void gserial_free_line(unsigned char port_num)

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Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

#syz test

diff --git a/drivers/usb/usbip/usbip_event.c b/drivers/usb/usbip/usbip_event.c
index 0e00c2d00..81d761891 100644
--- a/drivers/usb/usbip/usbip_event.c
+++ b/drivers/usb/usbip/usbip_event.c
@@ -115,7 +115,7 @@ void usbip_stop_eh(struct usbip_device *ud)
 	if (pending)
 		usbip_dbg_eh("usbip_eh waiting completion %lx\n", pending);
 
-	wait_event_interruptible(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE));
+	wait_event(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE));
 	usbip_dbg_eh("usbip_eh has stopped\n");
 }
 EXPORT_SYMBOL_GPL(usbip_stop_eh);

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Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

#syz test

diff --git a/drivers/usb/usbip/usbip_event.c b/drivers/usb/usbip/usbip_event.c
index 0e00c2d000f8..e498102e8b26 100644
--- a/drivers/usb/usbip/usbip_event.c
+++ b/drivers/usb/usbip/usbip_event.c
@@ -105,6 +105,11 @@ int usbip_start_eh(struct usbip_device *ud)
 }
 EXPORT_SYMBOL_GPL(usbip_start_eh);
 
+#define WORK_QUEUE_NAME "usbip_event"
+
+static struct workqueue_struct *usbip_queue;
+static DECLARE_WORK(usbip_work, event_handler);
+
 void usbip_stop_eh(struct usbip_device *ud)
 {
 	unsigned long pending = ud->event & ~USBIP_EH_BYE;
@@ -115,16 +120,12 @@ void usbip_stop_eh(struct usbip_device *ud)
 	if (pending)
 		usbip_dbg_eh("usbip_eh waiting completion %lx\n", pending);
 
-	wait_event_interruptible(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE));
+	wait_event(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE));
+	flush_workqueue(usbip_queue);
 	usbip_dbg_eh("usbip_eh has stopped\n");
 }
 EXPORT_SYMBOL_GPL(usbip_stop_eh);
 
-#define WORK_QUEUE_NAME "usbip_event"
-
-static struct workqueue_struct *usbip_queue;
-static DECLARE_WORK(usbip_work, event_handler);
-
 int usbip_init_eh(void)
 {
 	usbip_queue = create_singlethread_workqueue(WORK_QUEUE_NAME);

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Subject: Re: test patch
Author: syedtayyabfarooq08@gmail.com

#syz test

--- a/drivers/usb/usbip/usbip_event.c
+++ b/drivers/usb/usbip/usbip_event.c
@@ -105,6,11 @@ int usbip_start_eh(struct usbip_device *ud)
 }
 EXPORT_SYMBOL_GPL(usbip_start_eh);

+#define WORK_QUEUE_NAME "usbip_event"
+
+static struct workqueue_struct *usbip_queue;
+static DECLARE_WORK(usbip_work, event_handler);
+
 void usbip_stop_eh(struct usbip_device *ud)
 {
 	unsigned long pending = ud->event & ~USBIP_EH_BYE;
@@ -115,16 +120,12 @@ void usbip_stop_eh(struct usbip_device *ud)
 	if (pending)
 		usbip_dbg_eh("usbip_eh waiting completion %lx\n", pending);

-	wait_event_interruptible(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE));
+	wait_event(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE));
+	flush_workqueue(usbip_queue);
 	usbip_dbg_eh("usbip_eh has stopped\n");
 }
 EXPORT_SYMBOL_GPL(usbip_stop_eh);

-#define WORK_QUEUE_NAME "usbip_event"
-
-static struct workqueue_struct *usbip_queue;
-static DECLARE_WORK(usbip_work, event_handler);
-
 int usbip_init_eh(void)
 {
 	usbip_queue = create_singlethread_workqueue(WORK_QUEUE_NAME);