scsi: libsas: Fix SMP IO deadlock during HA resume
Impact
In the Linux kernel, the following vulnerability has been resolved:
Source excerpt · LinuxAffected packages
Affected products
Vendor version evidence. Product records are separate from automatic dependency matching.
Linux · Linux
Other versions: unaffected
| Version / range | Source status |
|---|---|
| 9e24b47ef81d43b3fb1b14294f09991640c79fcc to before c9fb89246d9922ac0a45d504adb03e0bb971310c | affected |
| 3dbbbf656b850c9c8de05df6ad4a1dfc6ff02845 to before 08b95ef36a64c3ae4490794bed3c35d0c3354e85 | affected |
| 3dbbbf656b850c9c8de05df6ad4a1dfc6ff02845 to before 81e097a064b28b4a1f6ca1a8b433e659c1bd64c0 | affected |
| 09357f067122e2e28ec52e27013a1660a1571618 | affected |
| e50a6523a603594a6d92cdecfe11997d639410a3 | affected |
| c391b5899dd46485a5893696c12ae3e95a3a7325 | affected |
| b9c44a14062093e9fc2d6bddc696cfceadb482d7 | affected |
| 6.18.44 to before 6.18.59 | affected |
| 6.1.183 to before 6.2 | affected |
| 6.6.151 to before 6.7 | affected |
| 6.12.103 to before 6.13 | affected |
| 7.1.8 to before 7.2 | affected |
Linux · Linux
Other versions: affected
| Version / range | Source status |
|---|---|
| 7.2 | affected |
| 0 to before 7.2 | unaffected |
| 6.18.59 through 6.18.* (inclusive) | unaffected |
| 7.2.13 through 7.2.* (inclusive) | unaffected |
| 7.3 through * (inclusive) | unaffected |
Original source description
In the Linux kernel, the following vulnerability has been resolved:
scsi: libsas: Fix SMP IO deadlock during HA resume
smp_execute_task_sg() calls pm_runtime_get_sync() on the host before issuing an SMP command. When that command is itself issued from the HA resume path, the get_sync() deadlocks: it waits for the ongoing resume (the device is RPM_RESUMING), while the resume is blocked in sas_drain_work() waiting for that same SMP IO to complete.
The deadlock needs an expander-attached SATA disk. During sas_resume_ha() -> sas_drain_work(), DISCE_RESUME -> sas_resume_sata() -> ata_sas_port_resume() requests ATA_EH_RESET, and the hard reset for such a disk is done via SMP PHY CONTROL (sas_ata_hard_reset() -> sas_phy_reset() -> sas_smp_phy_control() -> smp_execute_task_sg()). Direct-attached SATA resets through lldd_control_phy() and SSP devices use TMFs, so neither hits this.
Replace the get_sync()/put_sync() pair with pm_runtime_get_noresume()/pm_runtime_put(). smp_execute_task_sg() only needs to hold off autosuspend while the SMP is in flight, and it must not try to resume the host: a sync resume issued from the HA resume path itself is what deadlocks, and by the time sas_resume_ha() runs, hw_init has already reinitialized the hardware, so the device is accessible without one.
The usage reference is still required. Discovery work normally runs inside an event worker's PM reference, taken at sas_notify_port_event() notify time and held until the handler has flushed the disco queue. sas_rediscover_ex_phy() however requeues DISCE_REVALIDATE_DOMAIN from within the revalidation worker itself, and flush_workqueue() does not wait for work items queued during execution, so that chained revalidation runs with no outer PM reference - without the get_noresume(), its SMP could race autosuspend.
For the BSG path, sas_smp_handler() is the only caller which may find the host autosuspended: expander SMP requests do not go through any SCSI device request queue, so nothing else in that path holds the host awake. Resume it there with pm_runtime_resume_and_get() and check the result.