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Commit 47b9012e authored by Marc-André Lureau's avatar Marc-André Lureau Committed by Linus Torvalds
Browse files

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: default avatarMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: default avatarMike 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ff62a342

mm/shmem.c

+28 −19
Original line number Diff line number Diff line
@@ -2717,6 +2717,19 @@ static int shmem_wait_for_pins(struct address_space *mapping) 
	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 @@ 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_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 @@ static int memfd_add_seals(struct file *file, unsigned int seals) 


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);