Bug 2383491 (CVE-2025-38448)

Summary: CVE-2025-38448 kernel: usb: gadget: u_serial: Fix race condition in TTY wakeup
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-07-25 16:02:18 UTC 
In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: u_serial: Fix race condition in TTY wakeup

A race condition occurs when gs_start_io() calls either gs_start_rx() or
gs_start_tx(), as those functions briefly drop the port_lock for
usb_ep_queue(). This allows gs_close() and gserial_disconnect() to clear
port.tty and port_usb, respectively.

Use the null-safe TTY Port helper function to wake up TTY.

Example
  CPU1:			      CPU2:
  gserial_connect() // lock
  			      gs_close() // await lock
  gs_start_rx()     // unlock
  usb_ep_queue()
  			      gs_close() // lock, reset port.tty and unlock
  gs_start_rx()     // lock
  tty_wakeup()      // NPE
Comment 1 Jon Moroney 2025-07-25 17:22:16 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025072504-CVE-2025-38448-f242@gregkh/T