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a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Underflow of f_count needs to be more carefully detected than it currently is. The results of get_file() should be checked, but the first step is detection. Redefine f_count from atomic_long_t to refcount_long_t. Signed-off-by: Kees Cook --- Cc: Christian Brauner Cc: Alexander Viro Cc: Jan Kara Cc: linux-fsdevel@vger.kernel.org --- fs/file.c | 4 ++-- fs/file_table.c | 6 +++--- include/linux/fs.h | 6 +++--- 3 files changed, 8 insertions(+), 8 deletions(-) diff --git a/fs/file.c b/fs/file.c index 3b683b9101d8..570424dd634b 100644 --- a/fs/file.c +++ b/fs/file.c @@ -865,7 +865,7 @@ static struct file *__get_file_rcu(struct file __rcu **f) if (!file) return NULL; - if (unlikely(!atomic_long_inc_not_zero(&file->f_count))) + if (unlikely(!refcount_long_inc_not_zero(&file->f_count))) return ERR_PTR(-EAGAIN); file_reloaded = rcu_dereference_raw(*f); @@ -987,7 +987,7 @@ static inline struct file *__fget_files_rcu(struct files_struct *files, * barrier. We only really need an 'acquire' one to * protect the loads below, but we don't have that. */ - if (unlikely(!atomic_long_inc_not_zero(&file->f_count))) + if (unlikely(!refcount_long_inc_not_zero(&file->f_count))) continue; /* diff --git a/fs/file_table.c b/fs/file_table.c index 4f03beed4737..f29e7b94bca1 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -167,7 +167,7 @@ static int init_file(struct file *f, int flags, const struct cred *cred) * fget-rcu pattern users need to be able to handle spurious * refcount bumps we should reinitialize the reused file first. */ - atomic_long_set(&f->f_count, 1); + refcount_long_set(&f->f_count, 1); return 0; } @@ -470,7 +470,7 @@ static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput); void fput(struct file *file) { - if (atomic_long_dec_and_test(&file->f_count)) { + if (refcount_long_dec_and_test(&file->f_count)) { struct task_struct *task = current; if (unlikely(!(file->f_mode & (FMODE_BACKING | FMODE_OPENED)))) { @@ -503,7 +503,7 @@ void fput(struct file *file) */ void __fput_sync(struct file *file) { - if (atomic_long_dec_and_test(&file->f_count)) + if (refcount_long_dec_and_test(&file->f_count)) __fput(file); } diff --git a/include/linux/fs.h b/include/linux/fs.h index 210bbbfe9b83..b8f6cce7c39d 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1001,7 +1001,7 @@ struct file { */ spinlock_t f_lock; fmode_t f_mode; - atomic_long_t f_count; + refcount_long_t f_count; struct mutex f_pos_lock; loff_t f_pos; unsigned int f_flags; @@ -1038,7 +1038,7 @@ struct file_handle { static inline struct file *get_file(struct file *f) { - if (unlikely(!atomic_long_inc_not_zero(&f->f_count))) + if (unlikely(!refcount_long_inc_not_zero(&f->f_count))) return NULL; return f; } @@ -1046,7 +1046,7 @@ static inline struct file *get_file(struct file *f) struct file *get_file_rcu(struct file __rcu **f); struct file *get_file_active(struct file **f); -#define file_count(x) atomic_long_read(&(x)->f_count) +#define file_count(x) refcount_long_read(&(x)->f_count) #define MAX_NON_LFS ((1UL<<31) - 1)