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    Subject[PATCH v2 3/3] Wire UFFD up to SELinux
    From
    This change gives userfaultfd file descriptors a real security
    context, allowing policy to act on them.

    Signed-off-by: Daniel Colascione <dancol@google.com>
    ---
    fs/userfaultfd.c | 34 +++++++++++++++++++++++++++++-----
    1 file changed, 29 insertions(+), 5 deletions(-)

    diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
    index 07b0f6e03849..78ff5d898733 100644
    --- a/fs/userfaultfd.c
    +++ b/fs/userfaultfd.c
    @@ -76,6 +76,8 @@ struct userfaultfd_ctx {
    bool mmap_changing;
    /* mm with one ore more vmas attached to this userfaultfd_ctx */
    struct mm_struct *mm;
    + /* The inode that owns this context --- not a strong reference. */
    + const struct inode *owner;
    };

    struct userfaultfd_fork_ctx {
    @@ -1014,14 +1016,18 @@ static __poll_t userfaultfd_poll(struct file *file, poll_table *wait)
    }
    }

    +static const struct file_operations userfaultfd_fops;
    +
    static int resolve_userfault_fork(struct userfaultfd_ctx *ctx,
    struct userfaultfd_ctx *new,
    struct uffd_msg *msg)
    {
    int fd;

    - fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, new,
    - O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS));
    + fd = anon_inode_getfd_secure(
    + "[userfaultfd]", &userfaultfd_fops, new,
    + O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS),
    + ctx->owner);
    if (fd < 0)
    return fd;

    @@ -1918,7 +1924,7 @@ static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
    }
    #endif

    -const struct file_operations userfaultfd_fops = {
    +static const struct file_operations userfaultfd_fops = {
    #ifdef CONFIG_PROC_FS
    .show_fdinfo = userfaultfd_show_fdinfo,
    #endif
    @@ -1943,6 +1949,7 @@ static void init_once_userfaultfd_ctx(void *mem)

    SYSCALL_DEFINE1(userfaultfd, int, flags)
    {
    + struct file *file;
    struct userfaultfd_ctx *ctx;
    int fd;

    @@ -1972,8 +1979,25 @@ SYSCALL_DEFINE1(userfaultfd, int, flags)
    /* prevent the mm struct to be freed */
    mmgrab(ctx->mm);

    - fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, ctx,
    - O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
    + file = anon_inode_getfile_secure(
    + "[userfaultfd]", &userfaultfd_fops, ctx,
    + O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS),
    + NULL);
    + if (IS_ERR(file)) {
    + fd = PTR_ERR(file);
    + goto out;
    + }
    +
    + fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
    + if (fd < 0) {
    + fput(file);
    + goto out;
    + }
    +
    + ctx->owner = file_inode(file);
    + fd_install(fd, file);
    +
    +out:
    if (fd < 0) {
    mmdrop(ctx->mm);
    kmem_cache_free(userfaultfd_ctx_cachep, ctx);
    --
    2.25.1.696.g5e7596f4ac-goog
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