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filelock: add a new locks_inode_context accessor function

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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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
This commit is contained in:
Jeff Layton 2022-11-16 09:02:30 -05:00
parent ab1ddef98a
commit 401a8b8fd5
2 changed files with 26 additions and 12 deletions
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24
fs/locks.c
View File

@ -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;

14
include/linux/fs.h
View File

@ -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)