On 2024/12/6 20:58, Amir Goldstein wrote:
On Fri, Dec 6, 2024 at 11:45 AM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
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So maybe use mm_get_unmapped_area() instead of __get_unmapped_area(), something like below, +static unsigned long ovl_get_unmapped_area(struct file *file, + unsigned long addr, unsigned long len, unsigned long pgoff, + unsigned long flags) +{ + struct file *realfile; + const struct cred *old_cred; + + realfile = ovl_real_file(file); + if (IS_ERR(realfile)) + return PTR_ERR(realfile); + + if (realfile->f_op->get_unmapped_area) { + unsigned long ret; + + old_cred = ovl_override_creds(file_inode(file)->i_sb); + ret = realfile->f_op->get_unmapped_area(realfile, addr, len, + pgoff, flags); + ovl_revert_creds(old_cred); + + if (ret) + return ret; + } + + return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags); +} Correct me If I'm wrong.You just need to be aware of the fact that between ovl_get_unmapped_area() and ovl_mmap(), ovl_real_file(file) could change from the lower file, to the upper file due to another operation that initiated copy-up.
Not sure about this part(I have very little knowledge of ovl), do you mean that we could not use ovl_real_file()? The ovl_mmap() using realfile = file->private_data, we may use similar way in ovl_get_unmapped_area(). but I may have misunderstood. Thanks.
