[PATCH 0/1] sched: fix user_mask double free

[wangbiao3]

From: wangbiao3 <wangbiao3@xxxxxxxxxx>

    Clone/Fork a new task,call dup_task_struct->arch_dup_task_struct(tsk,orig)
    which copy the data of parent/sibling task inclding p->user_cpus_ptr,so
    the user_cpus_ptr of newtask is the same with orig task's.When
    dup_task_struct call dup_user_cpus_ptr(tsk, orig, node),it return 0
    dircetly if src->user_cpus_ptris free by other task,in this case ,
    the newtask's address of user_cpus_ptr is not changed. Finally,
    wakup newtask to execute, call task_cpu_possible_mask-->
    do_set_cpus_allowed to set new task's user_cpus_ptr(user_mask) which
    call kfree user_mask at the end. So cause a slub double free panic.

    Use pi_lock to protect content of user_cpus_ptr in dup_user_cpus_ptr and
    clear dst->user_cpus_ptr when found src->user_cpus_ptr is null

    kernel BUG at mm/slub.c:363!
    Call trace:
     __slab_free+0x230/0x28c
     kfree+0x220/0x2cc
     do_set_cpus_allowed+0x74/0xa4
     select_fallback_rq+0x12c/0x200
     wake_up_new_task+0x26c/0x304
     kernel_clone+0x2c0/0x470
     __arm64_sys_clone+0x5c/0x8c
     invoke_syscall+0x60/0x150
     el0_svc_common.llvm.13030543509303927816+0x98/0x114
     do_el0_svc_compat+0x20/0x30
     el0_svc_compat+0x28/0x90
     el0t_32_sync_handler+0x7c/0xbc
     el0t_32_sync+0x1b8/0x1bc


wangbiao3 (1):
  sched: fix user_mask double free

 kernel/sched/core.c | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

--
2.38.1

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