ALSA: usb-audio: Fix NULL pointer dereference in snd_usb_mixer_controls_badd

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: usb-audio: Fix NULL pointer dereference in snd_usb_mixer_controls_badd In snd_usb_create_streams(), for UAC version 3 devices, the Interface Association Descriptor (IAD) is retrieved via usb_ifnum_to_if(). If this call fails, a fallback routine attempts to obtain the IAD from the next interface and sets a BADD profile. However, snd_usb_mixer_controls_badd() assumes that the IAD retrieved from usb_ifnum_to_if() is always valid, without performing a NULL check. This can lead to a NULL pointer dereference when usb_ifnum_to_if() fails to find the interface descriptor. This patch adds a NULL pointer check after calling usb_ifnum_to_if() in snd_usb_mixer_controls_badd() to prevent the dereference. This issue was discovered by syzkaller, which triggered the bug by sending a crafted USB device descriptor.

References

• https://git.kernel.org/stable/c/23aea9c74aeea2625aaf4fbcc6beb9d09e30f9e4
• https://git.kernel.org/stable/c/c5c08965ab96b16361e69a1e2a0e89dbcb99b5a6
• https://git.kernel.org/stable/c/9f282104627be5fbded3102ff9004f753c55a063
• https://git.kernel.org/stable/c/2762d3ea9c929ca4094541ca517c317ffa94625b
• https://git.kernel.org/stable/c/57f607c112966c21240c424b33e2cb71e121dcf0
• https://git.kernel.org/stable/c/cbdbfc756f2990942138ed0138da9303b4dbf9ff
• https://git.kernel.org/stable/c/85568535893600024d7d8794f4f8b6428b521e0c
• https://git.kernel.org/stable/c/632108ec072ad64c8c83db6e16a7efee29ebfb74