CVE-2022-50045

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> powerpc/pci: Fix get_phb_number() locking<br /> <br /> The recent change to get_phb_number() causes a DEBUG_ATOMIC_SLEEP<br /> warning on some systems:<br /> <br /> BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580<br /> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper<br /> preempt_count: 1, expected: 0<br /> RCU nest depth: 0, expected: 0<br /> 1 lock held by swapper/1:<br /> #0: c157efb0 (hose_spinlock){+.+.}-{2:2}, at: pcibios_alloc_controller+0x64/0x220<br /> Preemption disabled at:<br /> [] 0x0<br /> CPU: 0 PID: 1 Comm: swapper Not tainted 5.19.0-yocto-standard+ #1<br /> Call Trace:<br /> [d101dc90] [c073b264] dump_stack_lvl+0x50/0x8c (unreliable)<br /> [d101dcb0] [c0093b70] __might_resched+0x258/0x2a8<br /> [d101dcd0] [c0d3e634] __mutex_lock+0x6c/0x6ec<br /> [d101dd50] [c0a84174] of_alias_get_id+0x50/0xf4<br /> [d101dd80] [c002ec78] pcibios_alloc_controller+0x1b8/0x220<br /> [d101ddd0] [c140c9dc] pmac_pci_init+0x198/0x784<br /> [d101de50] [c140852c] discover_phbs+0x30/0x4c<br /> [d101de60] [c0007fd4] do_one_initcall+0x94/0x344<br /> [d101ded0] [c1403b40] kernel_init_freeable+0x1a8/0x22c<br /> [d101df10] [c00086e0] kernel_init+0x34/0x160<br /> [d101df30] [c001b334] ret_from_kernel_thread+0x5c/0x64<br /> <br /> This is because pcibios_alloc_controller() holds hose_spinlock but<br /> of_alias_get_id() takes of_mutex which can sleep.<br /> <br /> The hose_spinlock protects the phb_bitmap, and also the hose_list, but<br /> it doesn&amp;#39;t need to be held while get_phb_number() calls the OF routines,<br /> because those are only looking up information in the device tree.<br /> <br /> So fix it by having get_phb_number() take the hose_spinlock itself, only<br /> where required, and then dropping the lock before returning.<br /> pcibios_alloc_controller() then needs to take the lock again before the<br /> list_add() but that&amp;#39;s safe, the order of the list is not important.