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Tue, 3 Nov 2026 14:47:43 +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 MW8OEQ/06WroEgAAD6G6ig (envelope-from ); Tue, 03 Nov 2026 14:47:43 +0000 Date: Tue, 03 Nov 2026 15:47:39 +0100 Message-ID: <87zevqvuno.wl-tiwai@suse.de> From: Takashi Iwai To: Sonali Pradhan Cc: nkapron@google.com, gregkh@linuxfoundation.org, tiwai@suse.de, balbi@kernel.org, jeffinphilip14@gmail.com, victor.krawiec@arturia.com, fanwu01@zju.edu.cn, christophe.jaillet@wanadoo.fr, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] usb: gadget: f_midi: fix UAF race during IN request handling In-Reply-To: <20261028074821.579450-1-sonalipradhan@google.com> References: <20261028074821.579450-1-sonalipradhan@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/30.2 Mule/6.0 X-Mailing-List: linux-kernel@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-Level: X-Spamd-Result: default: False [-12.30 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; 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]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com,wanadoo.fr]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[12]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FREEMAIL_CC(0.00)[google.com,linuxfoundation.org,suse.de,kernel.org,gmail.com,arturia.com,zju.edu.cn,wanadoo.fr,vger.kernel.org]; TO_DN_SOME(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:email] X-Spam-Score: -12.30 On Wed, 28 Oct 2026 08:48:21 +0100, Sonali Pradhan wrote: > > f_midi_disable() drains and frees pre-allocated IN requests from > in_req_fifo without holding midi->transmit_lock. If f_midi_transmit() > runs concurrently on the workqueue, f_midi_do_transmit() can peek a > request from in_req_fifo and write into its buffer while > f_midi_disable() frees it, leading to a use-after-free. > > Additionally, when usb_ep_queue() fails in f_midi_do_transmit() (such > as with -ESHUTDOWN when the endpoint is disabled concurrently), it > resets req->length = 0 and returns active instead of the error code, > causing the do-while loop in f_midi_transmit() to keep spinning under > midi->transmit_lock until the substream is drained. > > Fix this by acquiring midi->transmit_lock in f_midi_disable() while > releasing IN requests from in_req_fifo, and returning the error code > from f_midi_do_transmit() when usb_ep_queue() fails so f_midi_transmit() > aborts immediately and drops active substreams. > > Fixes: e1e3d7ec5da3 ("usb: gadget: f_midi: pre-allocate IN requests") > Cc: stable@vger.kernel.org > Signed-off-by: Sonali Pradhan Reviewed-by: Takashi Iwai thanks, Takashi > --- > Changes in v2: > - Remove the transmit_lock and ep->enabled checks added in v1 from > f_midi_complete() and f_midi_transmit(). > - Return error code from f_midi_do_transmit() when usb_ep_queue() fails > so f_midi_transmit() aborts the loop immediately. > - Link to v1: https://lore.kernel.org/all/20261019135701.2767078-1-sonalipradhan@google.com/ > > drivers/usb/gadget/function/f_midi.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c > index 63fb6ee70a3d..48cda34399e8 100644 > --- a/drivers/usb/gadget/function/f_midi.c > +++ b/drivers/usb/gadget/function/f_midi.c > @@ -420,6 +420,7 @@ static void f_midi_disable(struct usb_function *f) > struct f_midi *midi = func_to_midi(f); > struct usb_composite_dev *cdev = f->config->cdev; > struct usb_request *req = NULL; > + unsigned long flags; > > DBG(cdev, "disable\n"); > > @@ -431,8 +432,10 @@ static void f_midi_disable(struct usb_function *f) > usb_ep_disable(midi->out_ep); > > /* release IN requests */ > + spin_lock_irqsave(&midi->transmit_lock, flags); > while (kfifo_get(&midi->in_req_fifo, &req)) > free_ep_req(midi->in_ep, req); > + spin_unlock_irqrestore(&midi->transmit_lock, flags); > > f_midi_drop_out_substreams(midi); > } > @@ -661,6 +664,7 @@ static int f_midi_do_transmit(struct f_midi *midi, struct usb_ep *ep) > ERROR(midi, "%s failed to queue req: %d\n", > midi->in_ep->name, err); > req->length = 0; /* Re-use request next time. */ > + return err; > } else { > /* Upon success, put request at the back of the queue. */ > kfifo_skip(&midi->in_req_fifo); > -- > 2.56.0.307.g5fe7bd680c-goog