CVE-2023-53045
usb: gadget: u_audio: don't let userspace block driver unbind
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usb: gadget: u_audio: don't let userspace block driver unbind
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: u_audio: don't let userspace block driver unbind In the unbind callback for f_uac1 and f_uac2, a call to snd_card_free() via g_audio_cleanup() will disconnect the card and then wait for all resources to be released, which happens when the refcount falls to zero. Since userspace can keep the refcount incremented by not closing the relevant file descriptor, the call to unbind may block indefinitely. This can cause a deadlock during reboot, as evidenced by the following blocked task observed on my machine: task:reboot state:D stack:0 pid:2827 ppid:569 flags:0x0000000c Call trace: __switch_to+0xc8/0x140 __schedule+0x2f0/0x7c0 schedule+0x60/0xd0 schedule_timeout+0x180/0x1d4 wait_for_completion+0x78/0x180 snd_card_free+0x90/0xa0 g_audio_cleanup+0x2c/0x64 afunc_unbind+0x28/0x60 ... kernel_restart+0x4c/0xac __do_sys_reboot+0xcc/0x1ec __arm64_sys_reboot+0x28/0x30 invoke_syscall+0x4c/0x110 ... The issue can also be observed by opening the card with arecord and then stopping the process through the shell before unbinding: # arecord -D hw:UAC2Gadget -f S32_LE -c 2 -r 48000 /dev/null Recording WAVE '/dev/null' : Signed 32 bit Little Endian, Rate 48000 Hz, Stereo ^Z[1]+ Stopped arecord -D hw:UAC2Gadget -f S32_LE -c 2 -r 48000 /dev/null # echo gadget.0 > /sys/bus/gadget/drivers/configfs-gadget/unbind (observe that the unbind command never finishes) Fix the problem by using snd_card_free_when_closed() instead, which will still disconnect the card as desired, but defer the task of freeing the resources to the core once userspace closes its file descriptor.
Reserved 2025-04-16 | Published 2025-05-02 | Updated 2025-05-04 | Assigner Linuxgit.kernel.org/...c/3e016ef2e72da93a2ea7afbb45de1b481b44d761
git.kernel.org/...c/3256e152b645fc1e788ba44c2d8ced690113e3e6
git.kernel.org/...c/0eda2004f38d95ef5715d62be884cd344260535b
git.kernel.org/...c/33f341c1fc60e172a3515c51bdabee11e83d1ee9
git.kernel.org/...c/b131989797f7287d7fdadb2bababc05a15d44750
git.kernel.org/...c/3bc7324e4911351e39c54a62e6ca46321cb10faf
git.kernel.org/...c/43ca70753dfffd517d2af126da28690f8f615605
git.kernel.org/...c/6c67ed9ad9b83e453e808f9b31a931a20a25629b
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