A null-pointer dereference occurs in f_midi2_free_ep_reqs() when attempting to clean up an endpoint that was never initialized. When configuring the MIDI 2.0 gadget via configfs and setting the block direction to SNDRV_UMP_DIR_INPUT, the initialization of the midi1_ep_out endpoint is explicitly skipped during the gadget bind phase (f_midi2_bind()). As a result, the usb_ep->card field remains NULL. Later, when the host sets the alternate setting, f_midi2_set_alt() unconditionally stops both the IN and OUT endpoints by calling f_midi2_stop_eps(), which in turn calls f_midi2_free_ep_reqs() for both endpoints. When f_midi2_free_ep_reqs() is called for the uninitialized midi1_ep_out, it attempts to dereference usb_ep->card to determine the number of requests to free, leading to a crash. Fix this by using usb_ep->num_reqs instead of usb_ep->card->info.num_reqs in f_midi2_free_ep_reqs(). usb_ep->num_reqs is correctly set during f_midi2_init_ep() and remains 0 if the endpoint was never initialized, safely avoiding the loop. For consistency, apply the same change to f_midi2_alloc_ep_reqs(). Oops: general protection fault, probably for non-canonical address 0xdffffc00000000ee: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000770-0x0000000000000777] ... RIP: 0010:f_midi2_free_ep_reqs drivers/usb/gadget/function/f_midi2.c:1166 [inline] RIP: 0010:f_midi2_stop_eps+0x28e/0x4d0 drivers/usb/gadget/function/f_midi2.c:1246 ... Call Trace: f_midi2_set_alt+0x11c/0xf00 drivers/usb/gadget/function/f_midi2.c:1296 composite_setup+0x1ffd/0x3480 drivers/usb/gadget/composite.c:1933 configfs_composite_setup+0xbd/0x100 drivers/usb/gadget/configfs.c:1877 Fixes: 8b645922b223 ("usb: gadget: Add support for USB MIDI 2.0 function driver") Assisted-by: Gemini:gemini-3.5-flash Gemini:gemini-3.1-pro-preview syzbot Reported-by: syzbot+bbb6dad313f4aaa8da6b@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=bbb6dad313f4aaa8da6b Link: https://syzkaller.appspot.com/ai_job?id=8ce30b1a-8cf7-4e38-bcf7-1f69e6f6313f To: "Greg Kroah-Hartman" To: To: "Takashi Iwai" Cc: "Christophe JAILLET" Cc: "Kees Cook" Cc: --- diff --git a/drivers/usb/gadget/function/f_midi2.c b/drivers/usb/gadget/function/f_midi2.c index 19fdac024..5e54cf994 100644 --- a/drivers/usb/gadget/function/f_midi2.c +++ b/drivers/usb/gadget/function/f_midi2.c @@ -1145,7 +1145,7 @@ static int f_midi2_alloc_ep_reqs(struct f_midi2_usb_ep *usb_ep) if (!usb_ep->reqs) return -EINVAL; - for (i = 0; i < midi2->info.num_reqs; i++) { + for (i = 0; i < usb_ep->num_reqs; i++) { if (usb_ep->reqs[i].req) continue; usb_ep->reqs[i].req = alloc_ep_req(usb_ep->usb_ep, @@ -1160,10 +1160,9 @@ static int f_midi2_alloc_ep_reqs(struct f_midi2_usb_ep *usb_ep) /* Free allocated requests */ static void f_midi2_free_ep_reqs(struct f_midi2_usb_ep *usb_ep) { - struct f_midi2 *midi2 = usb_ep->card; int i; - for (i = 0; i < midi2->info.num_reqs; i++) { + for (i = 0; i < usb_ep->num_reqs; i++) { if (!usb_ep->reqs[i].req) continue; free_ep_req(usb_ep->usb_ep, usb_ep->reqs[i].req); base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff -- This is an AI-generated patch subject to moderation. Reply with '#syz upstream' to Sign-off the patch as a human author and send it to the upstream kernel mailing lists. Reply with '#syz reject' to reject it ('#syz unreject' to undo). See https://goo.gle/syzbot-ai-patches for information about AI-generated patches. You can comment on the patch as usual, syzbot will try to address the comments and send a new version of the patch if necessary. syzbot engineers can be reached at syzkaller@googlegroups.com.