Quoting Cyrill Gorcunov (gorcu...@openvz.org):
> Instead of taking mm->mmap_sem inside prctl_set_mm_exe_file move
> it out of and rename the helper to prctl_set_mm_exe_file_locked.
> This will allow to reuse this function in a next patch.
>
> Signed-off-by: Cyrill Gorcunov <gorcu...@openvz.org>
> Cc: Kees Cook <keesc...@chromium.org>
> Cc: Tejun Heo <t...@kernel.org>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: Andrew Vagin <ava...@openvz.org>
> Cc: Eric W. Biederman <ebied...@xmission.com>
> Cc: H. Peter Anvin <h...@zytor.com>
> Cc: Serge Hallyn <serge.hal...@canonical.com>
Acked-by: Serge Hallyn <serge.hal...@canonical.com>
> Cc: Pavel Emelyanov <xe...@parallels.com>
> Cc: Vasiliy Kulikov <seg...@openwall.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hir...@jp.fujitsu.com>
> Cc: Michael Kerrisk <mtk.manpa...@gmail.com>
> Cc: Julien Tinnes <j...@google.com>
> ---
> kernel/sys.c | 21 +++++++++++----------
> 1 file changed, 11 insertions(+), 10 deletions(-)
>
> Index: linux-2.6.git/kernel/sys.c
> ===================================================================
> --- linux-2.6.git.orig/kernel/sys.c
> +++ linux-2.6.git/kernel/sys.c
> @@ -1628,12 +1628,14 @@ SYSCALL_DEFINE1(umask, int, mask)
> return mask;
> }
>
> -static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
> +static int prctl_set_mm_exe_file_locked(struct mm_struct *mm, unsigned int
> fd)
> {
> struct fd exe;
> struct inode *inode;
> int err;
>
> + VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
> +
> exe = fdget(fd);
> if (!exe.file)
> return -EBADF;
> @@ -1654,8 +1656,6 @@ static int prctl_set_mm_exe_file(struct
> if (err)
> goto exit;
>
> - down_write(&mm->mmap_sem);
> -
> /*
> * Forbid mm->exe_file change if old file still mapped.
> */
> @@ -1667,7 +1667,7 @@ static int prctl_set_mm_exe_file(struct
> if (vma->vm_file &&
> path_equal(&vma->vm_file->f_path,
> &mm->exe_file->f_path))
> - goto exit_unlock;
> + goto exit;
> }
>
> /*
> @@ -1678,13 +1678,10 @@ static int prctl_set_mm_exe_file(struct
> */
> err = -EPERM;
> if (test_and_set_bit(MMF_EXE_FILE_CHANGED, &mm->flags))
> - goto exit_unlock;
> + goto exit;
>
> err = 0;
> set_mm_exe_file(mm, exe.file); /* this grabs a reference to exe.file */
> -exit_unlock:
> - up_write(&mm->mmap_sem);
> -
> exit:
> fdput(exe);
> return err;
> @@ -1703,8 +1700,12 @@ static int prctl_set_mm(int opt, unsigne
> if (!capable(CAP_SYS_RESOURCE))
> return -EPERM;
>
> - if (opt == PR_SET_MM_EXE_FILE)
> - return prctl_set_mm_exe_file(mm, (unsigned int)addr);
> + if (opt == PR_SET_MM_EXE_FILE) {
> + down_write(&mm->mmap_sem);
> + error = prctl_set_mm_exe_file_locked(mm, (unsigned int)addr);
> + up_write(&mm->mmap_sem);
> + return error;
> + }
>
> if (addr >= TASK_SIZE || addr < mmap_min_addr)
> return -EINVAL;
>
> --
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