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Tue, 20 Oct 2026 09:06:58 +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 2iNZCTIv12qzZQAAD6G6ig (envelope-from ); Tue, 20 Oct 2026 09:06:58 +0000 Date: Tue, 20 Oct 2026 11:06:57 +0200 Message-ID: <87a4o8ivv2.wl-tiwai@suse.de> From: Takashi Iwai To: Sonali Pradhan Cc: Greg Kroah-Hartman , Neill Kapron , Takashi Iwai , Christophe JAILLET , Fan Wu , Victor Krawiec , Felipe Balbi , "Felipe F. Tonello" , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH RESEND] usb: gadget: f_midi: fix UAF race during IN request handling In-Reply-To: <20261019135701.2767078-1-sonalipradhan@google.com> References: <20261019135701.2767078-1-sonalipradhan@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/30.2 Mule/6.0 X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Spam-Flag: NO X-Spam-Score: -3.30 X-Spam-Level: X-Spamd-Result: default: False [-3.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[12]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FREEMAIL_ENVRCPT(0.00)[wanadoo.fr]; FREEMAIL_CC(0.00)[linuxfoundation.org,google.com,suse.de,wanadoo.fr,zju.edu.cn,arturia.com,ti.com,felipetonello.com,vger.kernel.org]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo] On Mon, 19 Oct 2026 15:57:01 +0200, Sonali Pradhan wrote: > > f_midi_disable() frees pre-allocated IN requests from in_req_fifo > without holding midi->transmit_lock. Concurrent f_midi_transmit() or > f_midi_complete() calls can then access these request buffers after they > are freed, leading to a use-after-free. > > Fix this by acquiring midi->transmit_lock in f_midi_disable() while > releasing IN requests, and checking ep->enabled under midi->transmit_lock > in f_midi_transmit() and f_midi_complete() before modifying requests. > > Fixes: e1e3d7ec5da3 ("usb: gadget: f_midi: pre-allocate IN requests") > Cc: stable@vger.kernel.org > Signed-off-by: Sonali Pradhan > --- > Resending and rebasing on latest linux-next as I haven't received > feedback on my initial submission: > https://lore.kernel.org/all/20260819102709.212646-1-sonalipradhan@google.com/ > > drivers/usb/gadget/function/f_midi.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c > index 63fb6ee70a3d..c26d04eb9209 100644 > --- a/drivers/usb/gadget/function/f_midi.c > +++ b/drivers/usb/gadget/function/f_midi.c > @@ -280,9 +280,18 @@ f_midi_complete(struct usb_ep *ep, struct usb_request *req) > /* We received stuff. req is queued again, below */ > f_midi_handle_out_data(ep, req); > } else if (ep == midi->in_ep) { > + unsigned long flags; > + > /* Our transmit completed. See if there's more to go. > * f_midi_transmit eats req, don't queue it again. */ > + spin_lock_irqsave(&midi->transmit_lock, flags); > + if (!ep->enabled) { > + spin_unlock_irqrestore(&midi->transmit_lock, flags); > + return; > + } > req->length = 0; > + spin_unlock_irqrestore(&midi->transmit_lock, flags); > + Does this transmit_lock help here? As far as I see, the ep enable/disable itself is done outside the lock. > @@ -678,10 +690,11 @@ static void f_midi_transmit(struct f_midi *midi) > unsigned long flags; > > /* We only care about USB requests if IN endpoint is enabled */ > - if (!ep || !ep->enabled) > - goto drop_out; > - > spin_lock_irqsave(&midi->transmit_lock, flags); > + if (!ep || !ep->enabled) { > + spin_unlock_irqrestore(&midi->transmit_lock, flags); > + goto drop_out; > + } Ditto. thanks, Takashi