2.7 KiB
CVE-2024-57889
Description
In the Linux kernel, the following vulnerability has been resolved:pinctrl: mcp23s08: Fix sleeping in atomic context due to regmap lockingIf a device uses MCP23xxx IO expander to receive IRQs, the followingbug can happen: BUG: sleeping function called from invalid context at kernel/locking/mutex.c:283 in_atomic(): 1, irqs_disabled(): 1, non_block: 0, ... preempt_count: 1, expected: 0 ... Call Trace: ... __might_resched+0x104/0x10e __might_sleep+0x3e/0x62 mutex_lock+0x20/0x4c regmap_lock_mutex+0x10/0x18 regmap_update_bits_base+0x2c/0x66 mcp23s08_irq_set_type+0x1ae/0x1d6 __irq_set_trigger+0x56/0x172 __setup_irq+0x1e6/0x646 request_threaded_irq+0xb6/0x160 ...We observed the problem while experimenting with a touchscreen driver whichused MCP23017 IO expander (I2C).The regmap in the pinctrl-mcp23s08 driver uses a mutex for protection fromconcurrent accesses, which is the default for regmaps without .fast_io,.disable_locking, etc.mcp23s08_irq_set_type() calls regmap_update_bits_base(), and the latterlocks the mutex.However, __setup_irq() locks desc->lock spinlock before calling thesefunctions. As a result, the system tries to lock the mutex whole holdingthe spinlock.It seems, the internal regmap locks are not needed in this driver at all.mcp->lock seems to protect the regmap from concurrent accesses already,except, probably, in mcp_pinconf_get/set.mcp23s08_irq_set_type() and mcp23s08_irq_mask/unmask() are called underchip_bus_lock(), which calls mcp23s08_irq_bus_lock(). The latter takesmcp->lock and enables regmap caching, so that the potentially slow I2Caccesses are deferred until chip_bus_unlock().The accesses to the regmap from mcp23s08_probe_one() do not need additionallocking.In all remaining places where the regmap is accessed, exceptmcp_pinconf_get/set(), the driver already takes mcp->lock.This patch adds locking in mcp_pinconf_get/set() and disables internallocking in the regmap config. Among other things, it fixes the sleepingin atomic context described above.
POC
Reference
No PoCs from references.