Re: KMSAN: uninit-value in alauda_check_media

[Jaskaran Singh]

On Mon, 2019-10-07 at 12:39 -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    1e76a3e5 kmsan: replace __GFP_NO_KMSAN_SHADOW with
> kmsan_i..
> git tree:       https://github.com/google/kmsan.git master
> console output: 
> https://syzkaller.appspot.com/x/log.txt?x=1204cc63600000
> kernel config:  
> https://syzkaller.appspot.com/x/.config?x=f03c659d0830ab8d
> dashboard link: 
> https://syzkaller.appspot.com/bug?extid=e7d46eb426883fb97efd
> compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
> 80fee25776c2fb61e74c1ecb1a523375c2500b69)
> syz repro:      
> https://syzkaller.appspot.com/x/repro.syz?x=123c860d600000
> C reproducer:   
> https://syzkaller.appspot.com/x/repro.c?x=110631b7600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the
> commit:
> Reported-by: syzbot+e7d46eb426883fb97efd@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> =====================================================
> BUG: KMSAN: uninit-value in alauda_transport+0x462/0x57f0  
> drivers/usb/storage/alauda.c:1137
> CPU: 0 PID: 12279 Comm: usb-storage Not tainted 5.3.0-rc7+ #0
> Hardware name: Google Google Compute Engine/Google Compute Engine,
> BIOS  
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x191/0x1f0 lib/dump_stack.c:113
>   kmsan_report+0x13a/0x2b0 mm/kmsan/kmsan_report.c:108
>   __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250
>   alauda_check_media+0x344/0x3310 drivers/usb/storage/alauda.c:460
>   alauda_transport+0x462/0x57f0 drivers/usb/storage/alauda.c:1137
>   usb_stor_invoke_transport+0xf5/0x27e0
> drivers/usb/storage/transport.c:606
>   usb_stor_transparent_scsi_command+0x5d/0x70  
> drivers/usb/storage/protocol.c:108
>   usb_stor_control_thread+0xca6/0x11a0 drivers/usb/storage/usb.c:380
>   kthread+0x4b5/0x4f0 kernel/kthread.c:256
>   ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355
> 
> Local variable description: ----status@alauda_check_media
> Variable was created at:
>   alauda_check_media+0x8e/0x3310 drivers/usb/storage/alauda.c:454
>   alauda_transport+0x462/0x57f0 drivers/usb/storage/alauda.c:1137
> =====================================================
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 0 PID: 12279 Comm: usb-storage Tainted:
> G    B             5.3.0-rc7+  
> #0
> Hardware name: Google Google Compute Engine/Google Compute Engine,
> BIOS  
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x191/0x1f0 lib/dump_stack.c:113
>   panic+0x3c9/0xc1e kernel/panic.c:219
>   kmsan_report+0x2a2/0x2b0 mm/kmsan/kmsan_report.c:131
>   __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250
>   alauda_check_media+0x344/0x3310 drivers/usb/storage/alauda.c:460
>   alauda_transport+0x462/0x57f0 drivers/usb/storage/alauda.c:1137
>   usb_stor_invoke_transport+0xf5/0x27e0
> drivers/usb/storage/transport.c:606
>   usb_stor_transparent_scsi_command+0x5d/0x70  
> drivers/usb/storage/protocol.c:108
>   usb_stor_control_thread+0xca6/0x11a0 drivers/usb/storage/usb.c:380
>   kthread+0x4b5/0x4f0 kernel/kthread.c:256
>   ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
> 
> 
> ---
> This bug 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@xxxxxxxxxxxxxxxxx
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

#syz test: https://github.com/google/kmsan.git 1e76a3e5

diff --git a/drivers/usb/storage/alauda.c
b/drivers/usb/storage/alauda.c
index ddab2cd3d2e7..bb309b9ad65b 100644
--- a/drivers/usb/storage/alauda.c
+++ b/drivers/usb/storage/alauda.c
@@ -452,7 +452,7 @@ static int alauda_init_media(struct us_data *us)
 static int alauda_check_media(struct us_data *us)
 {
 	struct alauda_info *info = (struct alauda_info *) us->extra;
-	unsigned char status[2];
+	unsigned char *status = us->iobuf;
 	int rc;
 
 	rc = alauda_get_media_status(us, status);