Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
scsi: libsas: Fix use-after-free bug in smp_execute_task_sg()
When executing SMP task failed, the smp_execute_task_sg() calls del_timer() to delete “slow_task->timer”. However, if the timer handler sas_task_internal_timedout() is running, the del_timer() in smp_execute_task_sg() will not stop it and a UAF will happen. The process is shown below:
(thread 1) | (thread 2) smp_execute_task_sg() | sas_task_internal_timedout() … | del_timer() | … | … sas_free_task(task) | kfree(task->slow_task) //FREE| | task->slow_task->… //USE
Fix by calling del_timer_sync() in smp_execute_task_sg(), which makes sure the timer handler have finished before the “task->slow_task” is deallocated.
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 6 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , Oracle Linux 6 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , Ubuntu 16.04 ELS
- Affected packages:
- kernel @ 2.6.32 (+9 more)
In the Linux kernel, the following vulnerability has been resolved:
scsi: libsas: Fix use-after-free bug in smp_execute_task_sg()
When executing SMP task failed, the smp_execute_task_sg() calls del_timer() to delete “slow_task->timer”. However, if the timer handler sas_task_internal_timedout() is running, the del_timer() in smp_execute_task_sg() will not stop it and a UAF will happen. The process is shown below:
(thread 1) | (thread 2) smp_execute_task_sg() | sas_task_internal_timedout() … | del_timer() | … | … sas_free_task(task) | kfree(task->slow_task) //FREE| | task->slow_task->… //USE
Fix by calling del_timer_sync() in smp_execute_task_sg(), which makes sure the timer handler have finished before the “task->slow_task” is deallocated.