Commit 90b2433e authored by Maíra Canal's avatar Maíra Canal Committed by Al Viro
Browse files

seq_file: fix NULL pointer arithmetic warning 



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: default avatarMaíra Canal <maira.canal@usp.br>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 6692531d

fs/kernfs/file.c

+1 −6
Original line number Diff line number Diff line
@@ -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)

fs/seq_file.c

+2 −2
Original line number Diff line number Diff line
@@ -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)

include/linux/seq_file.h

+1 −0
Original line number Diff line number Diff line
@@ -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 *);