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    Subject[RFC][PATCH 2/3] exec: Simplify unshare_files

    Now that exec calls unshare_files after the point of no return there
    is no reason to return displaced.

    Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
    ---
    fs/coredump.c | 5 +----
    fs/exec.c | 5 +----
    include/linux/fdtable.h | 2 +-
    kernel/fork.c | 12 ++++++------
    4 files changed, 9 insertions(+), 15 deletions(-)

    diff --git a/fs/coredump.c b/fs/coredump.c
    index 1e2c87acac9b..968ee5744bf9 100644
    --- a/fs/coredump.c
    +++ b/fs/coredump.c
    @@ -546,7 +546,6 @@ void do_coredump(const siginfo_t *siginfo)
    struct cred *cred;
    int retval = 0;
    int ispipe;
    - struct files_struct *displaced;
    /* require nonrelative corefile path and be extra careful */
    bool need_suid_safe = false;
    bool core_dumped = false;
    @@ -747,11 +746,9 @@ void do_coredump(const siginfo_t *siginfo)
    }

    /* get us an unshared descriptor table; almost always a no-op */
    - retval = unshare_files(&displaced);
    + retval = unshare_files();
    if (retval)
    goto close_fail;
    - if (displaced)
    - put_files_struct(displaced);
    if (!dump_interrupted()) {
    file_start_write(cprm.file);
    core_dumped = binfmt->core_dump(&cprm);
    diff --git a/fs/exec.c b/fs/exec.c
    index 6f6167ec08eb..7eeffa7d98c6 100644
    --- a/fs/exec.c
    +++ b/fs/exec.c
    @@ -1252,7 +1252,6 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
    */
    int flush_old_exec(struct linux_binprm * bprm)
    {
    - struct files_struct *displaced;
    int retval;

    /*
    @@ -1292,11 +1291,9 @@ int flush_old_exec(struct linux_binprm * bprm)
    flush_thread();
    current->personality &= ~bprm->per_clear;

    - retval = unshare_files(&displaced);
    + retval = unshare_files();
    if (retval)
    goto out;
    - if (displaced)
    - put_files_struct(displaced);

    /*
    * We have to apply CLOEXEC before we change whether the process is
    diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
    index 41615f38bcff..e65379336c4c 100644
    --- a/include/linux/fdtable.h
    +++ b/include/linux/fdtable.h
    @@ -108,7 +108,7 @@ struct task_struct;
    struct files_struct *get_files_struct(struct task_struct *);
    void put_files_struct(struct files_struct *fs);
    void reset_files_struct(struct files_struct *);
    -int unshare_files(struct files_struct **);
    +int unshare_files(void);
    struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
    void do_close_on_exec(struct files_struct *);
    int iterate_fd(struct files_struct *, unsigned,
    diff --git a/kernel/fork.c b/kernel/fork.c
    index d896e9ca38b0..a06a609075eb 100644
    --- a/kernel/fork.c
    +++ b/kernel/fork.c
    @@ -2564,21 +2564,21 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
    * the exec layer of the kernel.
    */

    -int unshare_files(struct files_struct **displaced)
    +int unshare_files(void)
    {
    struct task_struct *task = current;
    - struct files_struct *copy = NULL;
    + struct files_struct *files, *copy = NULL;
    int error;

    error = unshare_fd(CLONE_FILES, &copy);
    - if (error || !copy) {
    - *displaced = NULL;
    + if (error || !copy)
    return error;
    - }
    - *displaced = task->files;
    +
    + files = task->files;
    task_lock(task);
    task->files = copy;
    task_unlock(task);
    + put_files_struct(files);
    return 0;
    }

    --
    2.17.1
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