From 90b2433edb6d995bd23d6adde753095b4ab26104 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ma=C3=ADra=20Canal?= Date: Mon, 31 Jan 2022 15:22:42 -0300 Subject: [PATCH] seq_file: fix NULL pointer arithmetic warning MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Implement conditional logic in order to replace NULL pointer arithmetic. The use of NULL pointer arithmetic was pointed out by clang with the following warning: fs/kernfs/file.c:128:15: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] return NULL + !*ppos; ~~~~ ^ fs/seq_file.c:559:14: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] return NULL + (*pos == 0); Signed-off-by: Maíra Canal Signed-off-by: Al Viro --- fs/kernfs/file.c | 7 +------ fs/seq_file.c | 4 ++-- include/linux/seq_file.h | 1 + 3 files changed, 4 insertions(+), 8 deletions(-) diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index 9414a7a60a9f..7aefaca876a0 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -120,13 +120,8 @@ static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos) if (next == ERR_PTR(-ENODEV)) kernfs_seq_stop_active(sf, next); return next; - } else { - /* - * The same behavior and code as single_open(). Returns - * !NULL if pos is at the beginning; otherwise, NULL. - */ - return NULL + !*ppos; } + return single_start(sf, ppos); } static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos) diff --git a/fs/seq_file.c b/fs/seq_file.c index f8e1f4ee87ff..7ab8a58c29b6 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -554,9 +554,9 @@ int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc) } EXPORT_SYMBOL(seq_dentry); -static void *single_start(struct seq_file *p, loff_t *pos) +void *single_start(struct seq_file *p, loff_t *pos) { - return NULL + (*pos == 0); + return *pos ? NULL : SEQ_START_TOKEN; } static void *single_next(struct seq_file *p, void *v, loff_t *pos) diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h index 88cc16444b43..60820ab511d2 100644 --- a/include/linux/seq_file.h +++ b/include/linux/seq_file.h @@ -162,6 +162,7 @@ int seq_dentry(struct seq_file *, struct dentry *, const char *); int seq_path_root(struct seq_file *m, const struct path *path, const struct path *root, const char *esc); +void *single_start(struct seq_file *, loff_t *); int single_open(struct file *, int (*)(struct seq_file *, void *), void *); int single_open_size(struct file *, int (*)(struct seq_file *, void *), void *, size_t); int single_release(struct inode *, struct file *);