CVE-2025-68339atm/fore200e: Fix possible data race in fore200e_open()

Official description

In the Linux kernel, the following vulnerability has been resolved: atm/fore200e: Fix possible data race in fore200e_open() Protect access to fore200e->available_cell_rate with rate_mtx lock in the error handling path of fore200e_open() to prevent a data race. The field fore200e->available_cell_rate is a shared resource used to track available bandwidth. It is concurrently accessed by fore200e_open(), fore200e_close(), and fore200e_change_qos(). In fore200e_open(), the lock rate_mtx is correctly held when subtracting vcc->qos.txtp.max_pcr from available_cell_rate to reserve bandwidth. However, if the subsequent call to fore200e_activate_vcin() fails, the function restores the reserved bandwidth by adding back to available_cell_rate without holding the lock. This introduces a race condition because available_cell_rate is a global device resource shared across all VCCs. If the error path in fore200e_open() executes concurrently with operations like fore200e_close() or fore200e_change_qos() on other VCCs, a read-modify-write race occurs. Specifically, the error path reads the rate without the lock. If another CPU acquires the lock and modifies the rate (e.g., releasing bandwidth in fore200e_close()) between this read and the subsequent write, the error path will overwrite the concurrent update with a stale value. This results in incorrect bandwidth accounting.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/1b60f42a639999c37da7f1fbfa1ad29cf4cbdd2d
• https://git.kernel.org/stable/c/bd1415efbab507b9b995918105eef953013449dd
• https://git.kernel.org/stable/c/ed34c70d88e2b8b9bc6c3ede88751186d6c6d5d1
• https://git.kernel.org/stable/c/9917ba597cf95f307778e495f71ff25a5064d167
• https://git.kernel.org/stable/c/667ac868823224374f819500adc5baa2889c7bc5
• https://git.kernel.org/stable/c/6610361458e7eb6502dd3182f586f91fcc218039
• https://git.kernel.org/stable/c/82fca3d8a4a34667f01ec2351a607135249c9cff