CVE-2026-53025

In the Linux kernel, the following vulnerability has been resolved:

greybus: raw: fix use-after-free on cdev close

This addresses a use-after-free bug when a raw bundle is disconnected but its chardev is still opened by an application. When the application releases the cdev, it causes the following panic when init on free is enabled (CONFIG_INIT_ON_FREE_DEFAULT_ON=y):

    refcount_t: underflow; use-after-free.
    WARNING: CPU: 0 PID: 139 at lib/refcount.c:28 refcount_warn_saturate+0xd0/0x130
     ...
    Call Trace:
     <TASK>
     cdev_put+0x18/0x30
     __fput+0x255/0x2a0
     __x64_sys_close+0x3d/0x80
     do_syscall_64+0xa4/0x290
     entry_SYSCALL_64_after_hwframe+0x77/0x7f

The cdev is contained in the gb_raw structure, which is freed in the disconnect operation. When the cdev is released at a later time, cdev_put gets an address that points to freed memory.

To fix this use-after-free, convert the struct device from a pointer to being embedded, that makes the lifetime of the cdev and of this device the same. Then, use cdev_device_add, which guarantees that the device wont be released until all references to the cdev have been released. Finally, delegate the freeing of the structure to the device release function, instead of freeing immediately in the disconnect callback.

Affected Software

References

• https://git.kernel.org/stable/c/983cc2c7efbce04ecbf6328448d895044dd6ab31
• https://git.kernel.org/stable/c/ef2d97c15b19b3489de01695bce478601e236c3e