CVE-2026-64251pwrseq: core: fix use-after-free in pwrseq_debugfs_seq_next()

Official description

In the Linux kernel, the following vulnerability has been resolved: pwrseq: core: fix use-after-free in pwrseq_debugfs_seq_next() pwrseq_debugfs_seq_next() declares 'next' with __free(put_device), which causes put_device() to be called on the returned pointer when the variable goes out of scope. This results in a use-after-free since the seq_file framework receives a pointer whose reference has already been dropped. Simply removing __free(put_device) would fix the UAF but would leak the reference acquired by bus_find_next_device(), as stop() only calls up_read(&pwrseq_sem) and never releases the device reference. Fix this by making the reference counting consistent across all seq_file callbacks, matching the standard pattern used by PCI and SCSI: - start(): use get_device() so it returns a referenced pointer. - next(): explicitly put_device(curr) to release the previous device's reference (no NULL check needed - the seq_file framework only calls next() while the previous return was non-NULL). - stop(): put_device(data) to release the last iterated device's reference, with a NULL guard since stop() may be called with NULL when start() returned NULL or next() reached end-of-sequence.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/ba0b9f04c7a5f9887b8ce672eaf049502c0548ec
• https://git.kernel.org/stable/c/e91df6d273445c03f5aa302bfe147eda33d45794
• https://git.kernel.org/stable/c/73569a44fca2992f0ca4a4c0104069741b9873a0
• https://git.kernel.org/stable/c/257595adf9dac15ae1edd9d07753fbc576a7583d