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    Subject[PATCH 1/4] kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve
    Date
    This changes kcmp_epoll_target to use the new exec_update_mutex
    instead of cred_guard_mutex.

    This should be safe, as the credentials are only used for reading,
    and furthermore ->mm and ->sighand are updated on execve,
    but only under the new exec_update_mutex.

    Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
    ---
    kernel/kcmp.c | 8 ++++----
    1 file changed, 4 insertions(+), 4 deletions(-)

    diff --git a/kernel/kcmp.c b/kernel/kcmp.c
    index a0e3d7a..b3ff928 100644
    --- a/kernel/kcmp.c
    +++ b/kernel/kcmp.c
    @@ -173,8 +173,8 @@ static int kcmp_epoll_target(struct task_struct *task1,
    /*
    * One should have enough rights to inspect task details.
    */
    - ret = kcmp_lock(&task1->signal->cred_guard_mutex,
    - &task2->signal->cred_guard_mutex);
    + ret = kcmp_lock(&task1->signal->exec_update_mutex,
    + &task2->signal->exec_update_mutex);
    if (ret)
    goto err;
    if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) ||
    @@ -229,8 +229,8 @@ static int kcmp_epoll_target(struct task_struct *task1,
    }

    err_unlock:
    - kcmp_unlock(&task1->signal->cred_guard_mutex,
    - &task2->signal->cred_guard_mutex);
    + kcmp_unlock(&task1->signal->exec_update_mutex,
    + &task2->signal->exec_update_mutex);
    err:
    put_task_struct(task1);
    put_task_struct(task2);
    --
    1.9.1
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