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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: Maíra Canal <maira.canal@usp.br>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Maíra Canal 2022-01-31 15:22:42 -03:00 committed by Al Viro
parent 6692531df6
commit 90b2433edb
3 changed files with 4 additions and 8 deletions
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7
fs/kernfs/file.c
View File

@ -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)

4
fs/seq_file.c
View File

@ -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)

1
include/linux/seq_file.h
View File

@ -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 *);