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Wed, 24 Jul 2024 07:21:29 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id ucHrMXmroGYyNQAAD6G6ig (envelope-from ); Wed, 24 Jul 2024 07:21:29 +0000 Date: Wed, 24 Jul 2024 09:22:04 +0200 Message-ID: <871q3jmezn.wl-tiwai@suse.de> From: Takashi Iwai To: Edward Adam Davis Cc: syzbot+78eccfb8b3c9a85fc6c5@syzkaller.appspotmail.com, linux-kernel@vger.kernel.org, linux-sound@vger.kernel.org, perex@perex.cz, syzkaller-bugs@googlegroups.com, tiwai@suse.com Subject: Re: [PATCH] ALSA: line6: init buf to zero In-Reply-To: References: <00000000000000949c061df288c5@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-0.81 / 50.00]; DWL_DNSWL_MED(-2.00)[suse.de:dkim]; SUSPICIOUS_RECIPS(1.50)[]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; FREEMAIL_TO(0.00)[qq.com]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[qq.com]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCPT_COUNT_SEVEN(0.00)[7]; TAGGED_RCPT(0.00)[78eccfb8b3c9a85fc6c5]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.de:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Spamd-Bar: / X-Rspamd-Queue-Id: 191CD1F74B X-Spam-Level: X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -0.81 On Wed, 24 Jul 2024 07:58:45 +0200, Edward Adam Davis wrote: > > Syzbot report KMSAN uninit-value warnings. > When alloc buffer for midi_buffer->buf, init mem to 0. > > Reported-and-tested-by: syzbot+78eccfb8b3c9a85fc6c5@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=78eccfb8b3c9a85fc6c5 > Signed-off-by: Edward Adam Davis > --- > sound/usb/line6/midibuf.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/sound/usb/line6/midibuf.c b/sound/usb/line6/midibuf.c > index e7f830f7526c..1b699cb3b38d 100644 > --- a/sound/usb/line6/midibuf.c > +++ b/sound/usb/line6/midibuf.c > @@ -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< -- --- a/sound/usb/line6/driver.c +++ b/sound/usb/line6/driver.c @@ -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;