shmem: add sealing support to hugetlb-backed memfd

Adapt add_seals()/get_seals() to work with hugetbfs-backed memory.

Teach memfd_create() to allow sealing operations on MFD_HUGETLB.

Link: http://lkml.kernel.org/r/20171107122800.25517-6-marcandre.lureau@redhat.com
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index 86d7e06ee8559b1c9e37ba973ee7751d0d31bcea..1907688b75ee0110253f3d96e1e3d7ea02433a2a 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2717,6 +2717,19 @@ continue_resched:
        return error;
 }
 
+static unsigned int *memfd_file_seals_ptr(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 @@ continue_resched:
 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_file_seals_ptr(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:
@@ -2794,10 +2811,9 @@ unlock:
 
 static int memfd_get_seals(struct file *file)
 {
-       if (file->f_op != &shmem_file_operations)
-               return -EINVAL;
+       unsigned int *seals = memfd_file_seals_ptr(file);
 
-       return SHMEM_I(file_inode(file))->seals;
+       return seals ? *seals : -EINVAL;
 }
 
 long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
@@ -3655,7 +3671,7 @@ 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;
@@ -3665,9 +3681,6 @@ 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)))
@@ -3720,12 +3733,8 @@ 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_file_seals_ptr(file);
+               *file_seals &= ~F_SEAL_SEAL;
        }
 
        fd_install(fd, file);