KMSAN: uninit-value in line6_midibuf_read
syzbot
syzbotHello,
syzbot found the following issue on:
HEAD commit: 2c9b3512402e Merge tag 'for-linus' of git://git.kernel.org.. git tree: upstream console+strace: https://syzkaller.appspot.com/x/log.txt?x=13b02fe9980000 kernel config: https://syzkaller.appspot.com/x/.config?x=6bfb33a8ad10458f dashboard link: https://syzkaller.appspot.com/bug?extid=78eccfb8b3c9a85fc6c5 compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14ee34ad980000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1157b8ad980000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f8543636ba6c/disk-2c9b3512.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/403c612b7ac5/vmlinux-2c9b3512.xz
kernel image: https://storage.googleapis.com/syzbot-assets/88dc686d170a/bzImage-2c9b3512.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
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BUG: KMSAN: uninit-value in line6_midibuf_read+0x76b/0x1050 sound/usb/line6/midibuf.c:185 line6_midibuf_read+0x76b/0x1050 sound/usb/line6/midibuf.c:185 line6_data_received+0x4be/0x7e0 sound/usb/line6/driver.c:306 __usb_hcd_giveback_urb+0x572/0x840 drivers/usb/core/hcd.c:1650 usb_hcd_giveback_urb+0x157/0x720 drivers/usb/core/hcd.c:1734 dummy_timer+0xd3f/0x6aa0 drivers/usb/gadget/udc/dummy_hcd.c:1987 __run_hrtimer kernel/time/hrtimer.c:1689 [inline] __hrtimer_run_queues+0x564/0xe40 kernel/time/hrtimer.c:1753 hrtimer_interrupt+0x3ab/0x1490 kernel/time/hrtimer.c:1815 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1032 [inline] __sysvec_apic_timer_interrupt+0xa6/0x3a0 arch/x86/kernel/apic/apic.c:1049 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline] sysvec_apic_timer_interrupt+0x7e/0x90 arch/x86/kernel/apic/apic.c:1043 asm_sysvec_apic_timer_interrupt+0x1f/0x30 arch/x86/include/asm/idtentry.h:702 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:94 [inline] rcu_read_unlock_sched include/linux/rcupdate.h:954 [inline] pfn_valid include/linux/mmzone.h:2032 [inline] kmsan_virt_addr_valid arch/x86/include/asm/kmsan.h:94 [inline] virt_to_page_or_null+0xf2/0x150 mm/kmsan/shadow.c:75 kmsan_get_metadata+0x146/0x1d0 mm/kmsan/shadow.c:143 kmsan_get_shadow_origin_ptr+0x4d/0xb0 mm/kmsan/shadow.c:102 get_shadow_origin_ptr mm/kmsan/instrumentation.c:36 [inline] __msan_metadata_ptr_for_load_8+0x24/0x40 mm/kmsan/instrumentation.c:92 on_stack+0x57/0x1b0 update_stack_state+0xc1/0x270 arch/x86/kernel/unwind_frame.c:228 unwind_next_frame+0x19a/0x470 arch/x86/kernel/unwind_frame.c:315 arch_stack_walk+0x1ec/0x2d0 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0xaa/0xe0 kernel/stacktrace.c:122 kmsan_save_stack_with_flags mm/kmsan/core.c:74 [inline] kmsan_internal_chain_origin+0x57/0xd0 mm/kmsan/core.c:183 __msan_chain_origin+0xc3/0x150 mm/kmsan/instrumentation.c:251 skb_clone+0x460/0x550 net/core/skbuff.c:2066 __tcp_transmit_skb+0x433/0x4880 net/ipv4/tcp_output.c:1312 tcp_transmit_skb net/ipv4/tcp_output.c:1484 [inline] tcp_write_xmit+0x3a3d/0x8f00 net/ipv4/tcp_output.c:2829 __tcp_push_pending_frames+0xc4/0x380 net/ipv4/tcp_output.c:3014 tcp_push+0x755/0x7a0 net/ipv4/tcp.c:747 tcp_sendmsg_locked+0x619d/0x6e20 net/ipv4/tcp.c:1322 tcp_sendmsg+0x49/0x90 net/ipv4/tcp.c:1354 inet_sendmsg+0x142/0x280 net/ipv4/af_inet.c:853 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x267/0x380 net/socket.c:745 sock_write_iter+0x368/0x3d0 net/socket.c:1160 new_sync_write fs/read_write.c:497 [inline] vfs_write+0xb2f/0x1550 fs/read_write.c:590 ksys_write+0x20f/0x4c0 fs/read_write.c:643 __do_sys_write fs/read_write.c:655 [inline] __se_sys_write fs/read_write.c:652 [inline] __x64_sys_write+0x93/0xe0 fs/read_write.c:652 x64_sys_call+0x3490/0x3c10 arch/x86/include/generated/asm/syscalls_64.h:2 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Uninit was created at:
slab_post_alloc_hook mm/slub.c:3985 [inline] slab_alloc_node mm/slub.c:4028 [inline] __do_kmalloc_node mm/slub.c:4148 [inline] __kmalloc_noprof+0x661/0xf30 mm/slub.c:4161 kmalloc_noprof include/linux/slab.h:685 [inline] line6_midibuf_init+0x43/0x180 sound/usb/line6/midibuf.c:51 line6_init_midi+0x3e7/0x670 sound/usb/line6/midi.c:284 line6_init_cap_control+0x54e/0x770 sound/usb/line6/driver.c:704 line6_probe+0xeae/0x1120 sound/usb/line6/driver.c:797 pod_probe+0x79/0x90 sound/usb/line6/pod.c:522 usb_probe_interface+0xd6f/0x1350 drivers/usb/core/driver.c:399 really_probe+0x4db/0xd90 drivers/base/dd.c:656 __driver_probe_device+0x2ab/0x5d0 drivers/base/dd.c:798 driver_probe_device+0x72/0x890 drivers/base/dd.c:828 __device_attach_driver+0x568/0x9e0 drivers/base/dd.c:956 bus_for_each_drv+0x403/0x620 drivers/base/bus.c:457 __device_attach+0x3c1/0x650 drivers/base/dd.c:1028 device_initial_probe+0x32/0x40 drivers/base/dd.c:1077 bus_probe_device+0x3dc/0x5c0 drivers/base/bus.c:532 device_add+0x13aa/0x1ba0 drivers/base/core.c:3679 usb_set_configuration+0x31c9/0x38d0 drivers/usb/core/message.c:2210 usb_generic_driver_probe+0x109/0x2a0 drivers/usb/core/generic.c:254 usb_probe_device+0x3a7/0x690 drivers/usb/core/driver.c:294 really_probe+0x4db/0xd90 drivers/base/dd.c:656 __driver_probe_device+0x2ab/0x5d0 drivers/base/dd.c:798 driver_probe_device+0x72/0x890 drivers/base/dd.c:828 __device_attach_driver+0x568/0x9e0 drivers/base/dd.c:956 bus_for_each_drv+0x403/0x620 drivers/base/bus.c:457 __device_attach+0x3c1/0x650 drivers/base/dd.c:1028 device_initial_probe+0x32/0x40 drivers/base/dd.c:1077 bus_probe_device+0x3dc/0x5c0 drivers/base/bus.c:532 device_add+0x13aa/0x1ba0 drivers/base/core.c:3679 usb_new_device+0x15f4/0x2470 drivers/usb/core/hub.c:2651 hub_port_connect drivers/usb/core/hub.c:5521 [inline] hub_port_connect_change drivers/usb/core/hub.c:5661 [inline] port_event drivers/usb/core/hub.c:5821 [inline] hub_event+0x4ff8/0x72d0 drivers/usb/core/hub.c:5903 process_one_work kernel/workqueue.c:3231 [inline] process_scheduled_works+0xae0/0x1c40 kernel/workqueue.c:3312 worker_thread+0xea5/0x1520 kernel/workqueue.c:3390 kthread+0x3e2/0x540 kernel/kthread.c:389 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 CPU: 0 PID: 5052 Comm: sshd Not tainted 6.10.0-syzkaller-11185-g2c9b3512402e #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024 =====================================================
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when alloc buffer for midi_buffer->buf, init mem to 0
#syz test: upstream 2c9b3512402e
sound/usb/line6/midibuf.c +1 -1
@@ -48,7 +48,7 @@ void line6_midibuf_reset(struct midi_buffer *this)int line6_midibuf_init (struct midi_buffer *this,int size,int split) { - this->buf =kmalloc (size,GFP_KERNEL ); + this->buf =kzalloc (size,GFP_KERNEL );if (this->buf ==NULL )return -ENOMEM ;
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Hello,
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Tested on:
commit: 2c9b3512 Merge tag 'for-linus' of git://git.kernel.org.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=1481653d980000 kernel config: https://syzkaller.appspot.com/x/.config?x=6bfb33a8ad10458f dashboard link: https://syzkaller.appspot.com/bug?extid=78eccfb8b3c9a85fc6c5 compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 patch: https://syzkaller.appspot.com/x/patch.diff?x=133b2af1980000
Note: testing is done by a robot and is best-effort only.
PATCH 1/1 ALSA: line6: init buf to zero
In reply to syzbotSyzbot report KMSAN uninit-value warnings. When alloc buffer for midi_buffer->buf, init mem to 0.
--- sound/usb/line6/midibuf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
sound/usb/line6/midibuf.c +1 -1
@@ -48,7 +48,7 @@ void line6_midibuf_reset(struct midi_buffer *this)int line6_midibuf_init (struct midi_buffer *this,int size,int split) { - this->buf =kmalloc (size,GFP_KERNEL ); + this->buf =kzalloc (size,GFP_KERNEL );if (this->buf ==NULL )return -ENOMEM ;
Signature · 1 line
2.43.0
Re: [PATCH] ALSA: line6: init buf to zero
Quoted 16 lines · Edward Adam Davis
Syzbot report KMSAN uninit-value warnings. When alloc buffer for
midi_buffer->buf, init mem to 0.Reported-and-tested-by [email protected]Signed-off-by Edward Adam Davis <[email protected]>--- sound/usb/line6/midibuf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)sound/usb/line6/midibuf.c +0
-0
sound/usb/line6/midibuf.c void line6_midibuf_reset(struct midi_buffer *this) · line 51
Quoted 5 lines
sound/usb/line6/midibuf.c +1
-1@@ -48,7 +48,7 @@ void line6_midibuf_reset(struct midi_buffer *this)int line6_midibuf_init (struct midi_buffer *this,int size,int split) { - this->buf =kmalloc (size,GFP_KERNEL ); + this->buf =kzalloc (size,GFP_KERNEL );
Thanks for the patch. But this just hides the KMSAN warning, and it doesn't really address the cause - why it was exposed at all; the driver code had already a check and should have accessed only the updated data, but by some reason it slipped.
Through a quick glance, I see a possible. If that's the cause, the patch like below might help. I checked the reproducer locally but couldn't trigger the bug on my image, unfortunately, so it's just a wild guess, and it might be shooting a wrong way. Let's see.
thanks,
Takashi
-- 8< --
sound/usb/line6/driver.c +5 -0
@@ -286,12 +286,14 @@ static void line6_data_received(struct urb *urb) {struct usb_line6 *line6 = (struct usb_line6 *)urb->context;struct midi_buffer *mb = &line6->line6midi->midibuf_in; +unsigned long flags;int done;if (urb->status == -ESHUTDOWN )return ;if (line6->properties->capabilities &LINE6_CAP_CONTROL_MIDI ) { +spin_lock_irqsave (&line6->line6midi->lock, flags); done =line6_midibuf_write (mb, urb->transfer_buffer, urb->actual_length);
@@ -300,12 +302,15 @@ static void line6_data_received(struct urb *urb)dev_dbg (line6->ifcdev,"%d %d buffer overflow - message skipped\n" , done, urb->actual_length); } +spin_unlock_irqrestore (&line6->line6midi->lock, flags);for (;;) { +spin_lock_irqsave (&line6->line6midi->lock, flags); done =line6_midibuf_read (mb, line6->buffer_message,LINE6_MIDI_MESSAGE_MAXLEN ,LINE6_MIDIBUF_READ_RX ); +spin_unlock_irqrestore (&line6->line6midi->lock, flags);if (done <=0 )break ;