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f0efaf1872
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:
<TASK>
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: 8b645922b2 ("usb: gadget: Add support for USB MIDI 2.0 function driver")
Cc: stable <stable@kernel.org>
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
Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Closes: https://syzkaller.appspot.com/bug?extid=01a17afb30637396955e
Link: https://patch.msgid.link/cafe65f4-e1bb-46a3-901d-732814b861b2@mail.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>