Commit 401a8b8f authored by Jeff Layton's avatar Jeff Layton
Browse files

filelock: add a new locks_inode_context accessor function 



There are a number of places in the kernel that are accessing the
inode->i_flctx field without smp_load_acquire. This is required to
ensure that the caller doesn't see a partially-initialized structure.

Add a new accessor function for it to make this clear and convert all of
the relevant accesses in locks.c to use it. Also, convert
locks_free_lock_context to use the helper as well instead of just doing
a "bare" assignment.

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJeff Layton <jlayton@kernel.org>
parent ab1ddef9

fs/locks.c

+12 −12
Original line number Diff line number Diff line
@@ -175,7 +175,7 @@ locks_get_lock_context(struct inode *inode, int type) 
	struct file_lock_context *ctx;



	/* paired with cmpxchg() below */

	ctx = smp_load_acquire(&inode->i_flctx);

	ctx = locks_inode_context(inode);

	if (likely(ctx) || type == F_UNLCK)

		goto out;
@@ -194,7 +194,7 @@ locks_get_lock_context(struct inode *inode, int type) 
	 */

	if (cmpxchg(&inode->i_flctx, NULL, ctx)) {

		kmem_cache_free(flctx_cache, ctx);

		ctx = smp_load_acquire(&inode->i_flctx);

		ctx = locks_inode_context(inode);

	}

out:

	trace_locks_get_lock_context(inode, type, ctx);
@@ -247,7 +247,7 @@ locks_check_ctx_file_list(struct file *filp, struct list_head *list, 
void

locks_free_lock_context(struct inode *inode)

{

	struct file_lock_context *ctx = inode->i_flctx;

	struct file_lock_context *ctx = locks_inode_context(inode);



	if (unlikely(ctx)) {

		locks_check_ctx_lists(inode);
@@ -891,7 +891,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl) 
	void *owner;

	void (*func)(void);



	ctx = smp_load_acquire(&inode->i_flctx);

	ctx = locks_inode_context(inode);

	if (!ctx || list_empty_careful(&ctx->flc_posix)) {

		fl->fl_type = F_UNLCK;

		return;
@@ -1483,7 +1483,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type) 
	new_fl->fl_flags = type;



	/* typically we will check that ctx is non-NULL before calling */

	ctx = smp_load_acquire(&inode->i_flctx);

	ctx = locks_inode_context(inode);

	if (!ctx) {

		WARN_ON_ONCE(1);

		goto free_lock;
@@ -1588,7 +1588,7 @@ void lease_get_mtime(struct inode *inode, struct timespec64 *time) 
	struct file_lock_context *ctx;

	struct file_lock *fl;



	ctx = smp_load_acquire(&inode->i_flctx);

	ctx = locks_inode_context(inode);

	if (ctx && !list_empty_careful(&ctx->flc_lease)) {

		spin_lock(&ctx->flc_lock);

		fl = list_first_entry_or_null(&ctx->flc_lease,
@@ -1634,7 +1634,7 @@ int fcntl_getlease(struct file *filp) 
	int type = F_UNLCK;

	LIST_HEAD(dispose);



	ctx = smp_load_acquire(&inode->i_flctx);

	ctx = locks_inode_context(inode);

	if (ctx && !list_empty_careful(&ctx->flc_lease)) {

		percpu_down_read(&file_rwsem);

		spin_lock(&ctx->flc_lock);
@@ -1823,7 +1823,7 @@ static int generic_delete_lease(struct file *filp, void *owner) 
	struct file_lock_context *ctx;

	LIST_HEAD(dispose);



	ctx = smp_load_acquire(&inode->i_flctx);

	ctx = locks_inode_context(inode);

	if (!ctx) {

		trace_generic_delete_lease(inode, NULL);

		return error;
@@ -2563,7 +2563,7 @@ void locks_remove_posix(struct file *filp, fl_owner_t owner) 
	 * posix_lock_file().  Another process could be setting a lock on this

	 * file at the same time, but we wouldn't remove that lock anyway.

	 */

	ctx =  smp_load_acquire(&inode->i_flctx);

	ctx = locks_inode_context(inode);

	if (!ctx || list_empty(&ctx->flc_posix))

		return;
@@ -2636,7 +2636,7 @@ void locks_remove_file(struct file *filp) 
{

	struct file_lock_context *ctx;



	ctx = smp_load_acquire(&locks_inode(filp)->i_flctx);

	ctx = locks_inode_context(locks_inode(filp));

	if (!ctx)

		return;
@@ -2684,7 +2684,7 @@ bool vfs_inode_has_locks(struct inode *inode) 
	struct file_lock_context *ctx;

	bool ret;



	ctx = smp_load_acquire(&inode->i_flctx);

	ctx = locks_inode_context(inode);

	if (!ctx)

		return false;
@@ -2865,7 +2865,7 @@ void show_fd_locks(struct seq_file *f, 
	struct file_lock_context *ctx;

	int id = 0;



	ctx = smp_load_acquire(&inode->i_flctx);

	ctx = locks_inode_context(inode);

	if (!ctx)

		return;

include/linux/fs.h

+14 −0
Original line number Diff line number Diff line
@@ -1187,6 +1187,13 @@ extern void show_fd_locks(struct seq_file *f, 
			 struct file *filp, struct files_struct *files);

extern bool locks_owner_has_blockers(struct file_lock_context *flctx,

			fl_owner_t owner);



static inline struct file_lock_context *

locks_inode_context(const struct inode *inode)

{

	return smp_load_acquire(&inode->i_flctx);

}



#else /* !CONFIG_FILE_LOCKING */

static inline int fcntl_getlk(struct file *file, unsigned int cmd,

			      struct flock __user *user)
@@ -1332,6 +1339,13 @@ static inline bool locks_owner_has_blockers(struct file_lock_context *flctx, 
{

	return false;

}



static inline struct file_lock_context *

locks_inode_context(const struct inode *inode)

{

	return NULL;

}



#endif /* !CONFIG_FILE_LOCKING */



static inline struct inode *file_inode(const struct file *f)