CVE-2024-26605

In the Linux kernel, the following vulnerability has been resolved:
PCI/ASPM: Fix deadlock when enabling ASPM A last minute revert in 6.7-final
introduced a potential deadlock when enabling ASPM during probe of Qualcomm
PCIe controllers as reported by lockdep:
============================================ WARNING: possible recursive
locking detected 6.7.0 #40 Not tainted
-------------------------------------------- kworker/u16:5/90 is trying to
acquire lock: ffffacfa78ced000 (pci_bus_sem){++++}-{3:3}, at:
pcie_aspm_pm_state_change+0x58/0xdc but task is already holding lock:
ffffacfa78ced000 (pci_bus_sem){++++}-{3:3}, at: pci_walk_bus+0x34/0xbc
other info that might help us debug this: Possible unsafe locking scenario:
CPU0 ---- lock(pci_bus_sem); lock(pci_bus_sem); *** DEADLOCK*** Call
trace: print_deadlock_bug+0x25c/0x348 __lock_acquire+0x10a4/0x2064
lock_acquire+0x1e8/0x318 down_read+0x60/0x184
pcie_aspm_pm_state_change+0x58/0xdc pci_set_full_power_state+0xa8/0x114
pci_set_power_state+0xc4/0x120 qcom_pcie_enable_aspm+0x1c/0x3c [pcie_qcom]
pci_walk_bus+0x64/0xbc qcom_pcie_host_post_init_2_7_0+0x28/0x34 [pcie_qcom]
The deadlock can easily be reproduced on machines like the Lenovo ThinkPad
X13s by adding a delay to increase the race window during asynchronous
probe where another thread can take a write lock. Add a new
pci_set_power_state_locked() and associated helper functions that can be
called with the PCI bus semaphore held to avoid taking the read lock twice.