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    SubjectRe: [PATCH 09/10] VFS: Remove read-only checks from dentry_permission
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    On Mon, 06 Sep 2010, NeilBrown wrote:
    > It is not sufficient to depend on the the "filesystem is readonly"
    > tests in dentry_permission as it does not check if the vfsmnt is
    > readonly.
    > All call sites already call mnt_want_write or __mnt_is_readonly which
    > includes the test on MS_RDONLY.

    Last time I checked I found some holes (in nfsd IIRC). That was a
    long time ago and things may have changed.

    That check could be replaced with a

    if (IS_RDONLY(inode) &&
    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
    BUG();

    which would catch these cases but only if the superblock was marked
    r/o. Otherwise it's basically impossible to make sure the callers of
    the VFS play by the rules. That was one reason I advocated a
    path_... interface for the VFS instead of the current dentry based
    one, but Al didn't like it.

    Thanks,
    Miklos


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