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    Subject[PATCH 5/6] shmem: add sealing support to hugetlb-backed memfd
    Date
    Adapt add_seals()/get_seals() to work with hugetbfs-backed memory.

    Teach memfd_create() to allow sealing operations on MFD_HUGETLB.

    Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
    ---
    mm/shmem.c | 51 ++++++++++++++++++++++++++++++---------------------
    1 file changed, 30 insertions(+), 21 deletions(-)

    diff --git a/mm/shmem.c b/mm/shmem.c
    index b7811979611f..b7c59d993c19 100644
    --- a/mm/shmem.c
    +++ b/mm/shmem.c
    @@ -2717,6 +2717,19 @@ static int shmem_wait_for_pins(struct address_space *mapping)
    return error;
    }

    +static unsigned int *memfd_get_seals(struct file *file)
    +{
    + if (file->f_op == &shmem_file_operations)
    + return &SHMEM_I(file_inode(file))->seals;
    +
    +#ifdef CONFIG_HUGETLBFS
    + if (file->f_op == &hugetlbfs_file_operations)
    + return &HUGETLBFS_I(file_inode(file))->seals;
    +#endif
    +
    + return NULL;
    +}
    +
    #define F_ALL_SEALS (F_SEAL_SEAL | \
    F_SEAL_SHRINK | \
    F_SEAL_GROW | \
    @@ -2725,7 +2738,7 @@ static int shmem_wait_for_pins(struct address_space *mapping)
    static int memfd_add_seals(struct file *file, unsigned int seals)
    {
    struct inode *inode = file_inode(file);
    - struct shmem_inode_info *info = SHMEM_I(inode);
    + unsigned int *file_seals;
    int error;

    /*
    @@ -2758,8 +2771,6 @@ static int memfd_add_seals(struct file *file, unsigned int seals)
    * other file types.
    */

    - if (file->f_op != &shmem_file_operations)
    - return -EINVAL;
    if (!(file->f_mode & FMODE_WRITE))
    return -EPERM;
    if (seals & ~(unsigned int)F_ALL_SEALS)
    @@ -2767,12 +2778,18 @@ static int memfd_add_seals(struct file *file, unsigned int seals)

    inode_lock(inode);

    - if (info->seals & F_SEAL_SEAL) {
    + file_seals = memfd_get_seals(file);
    + if (!file_seals) {
    + error = -EINVAL;
    + goto unlock;
    + }
    +
    + if (*file_seals & F_SEAL_SEAL) {
    error = -EPERM;
    goto unlock;
    }

    - if ((seals & F_SEAL_WRITE) && !(info->seals & F_SEAL_WRITE)) {
    + if ((seals & F_SEAL_WRITE) && !(*file_seals & F_SEAL_WRITE)) {
    error = mapping_deny_writable(file->f_mapping);
    if (error)
    goto unlock;
    @@ -2784,7 +2801,7 @@ static int memfd_add_seals(struct file *file, unsigned int seals)
    }
    }

    - info->seals |= seals;
    + *file_seals |= seals;
    error = 0;

    unlock:
    @@ -2792,12 +2809,11 @@ static int memfd_add_seals(struct file *file, unsigned int seals)
    return error;
    }

    -static int memfd_get_seals(struct file *file)
    +static int memfd_fcntl_get_seals(struct file *file)
    {
    - if (file->f_op != &shmem_file_operations)
    - return -EINVAL;
    + unsigned int *seals = memfd_get_seals(file);

    - return SHMEM_I(file_inode(file))->seals;
    + return seals ? *seals : -EINVAL;
    }

    long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
    @@ -2813,7 +2829,7 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
    error = memfd_add_seals(file, arg);
    break;
    case F_GET_SEALS:
    - error = memfd_get_seals(file);
    + error = memfd_fcntl_get_seals(file);
    break;
    default:
    error = -EINVAL;
    @@ -3657,7 +3673,7 @@ SYSCALL_DEFINE2(memfd_create,
    const char __user *, uname,
    unsigned int, flags)
    {
    - struct shmem_inode_info *info;
    + unsigned int *file_seals;
    struct file *file;
    int fd, error;
    char *name;
    @@ -3667,9 +3683,6 @@ SYSCALL_DEFINE2(memfd_create,
    if (flags & ~(unsigned int)MFD_ALL_FLAGS)
    return -EINVAL;
    } else {
    - /* Sealing not supported in hugetlbfs (MFD_HUGETLB) */
    - if (flags & MFD_ALLOW_SEALING)
    - return -EINVAL;
    /* Allow huge page size encoding in flags. */
    if (flags & ~(unsigned int)(MFD_ALL_FLAGS |
    (MFD_HUGE_MASK << MFD_HUGE_SHIFT)))
    @@ -3722,12 +3735,8 @@ SYSCALL_DEFINE2(memfd_create,
    file->f_flags |= O_RDWR | O_LARGEFILE;

    if (flags & MFD_ALLOW_SEALING) {
    - /*
    - * flags check at beginning of function ensures
    - * this is not a hugetlbfs (MFD_HUGETLB) file.
    - */
    - info = SHMEM_I(file_inode(file));
    - info->seals &= ~F_SEAL_SEAL;
    + file_seals = memfd_get_seals(file);
    + *file_seals &= ~F_SEAL_SEAL;
    }

    fd_install(fd, file);
    --
    2.15.0.rc0.40.gaefcc5f6f
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