[PATCH 2/2] vsprintf: don't dereference pointers to the first or last page

Adam Borowski
2018-03-06T18:12:04Z

As old code to avoid so is inconsistent, let's unify it within a single
macro.

Signed-off-by: Adam Borowski <kilobyte@angband.pl>
---
lib/vsprintf.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 1c2c3cc5a321..4914dac03f0a 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -47,6 +47,8 @@
#include <linux/string_helpers.h>
#include "kstrtox.h"

+#define IS_BAD_PTR(x) ((unsigned long)(x) >= (unsigned long)-PAGE_SIZE \
+ || (unsigned long)(x) < PAGE_SIZE)
#define BAD_PTR_STRING(x) (!(x) ? "(null)" : IS_ERR(x) ? "(err)" : "(invalid)")

/**
@@ -589,7 +591,7 @@ char *string(char *buf, char *end, const char *s, struct printf_spec spec)
int len = 0;
size_t lim = spec.precision;

- if ((unsigned long)s < PAGE_SIZE)
+ if (IS_BAD_PTR(s))
s = BAD_PTR_STRING(s);

while (lim--) {
@@ -1583,7 +1585,7 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
if (!IS_ENABLED(CONFIG_OF))
return string(buf, end, "(!OF)", spec);

- if ((unsigned long)dn < PAGE_SIZE)
+ if (IS_BAD_PTR(dn))
return string(buf, end, BAD_PTR_STRING(dn), spec);

/* simple case without anything any more format specifiers */
@@ -1851,7 +1853,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
{
const int default_width = 2 * sizeof(void *);

- if (!ptr && *fmt != 'K' && *fmt != 'x') {
+ if (IS_BAD_PTR(ptr) && *fmt != 'K' && *fmt != 'x') {
/*
* Print (null)/etc with the same width as a pointer so it
* makes tabular output look nice.
@@ -2575,8 +2577,7 @@ int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args)
const char *save_str = va_arg(args, char *);
size_t len;

- if ((unsigned long)save_str > (unsigned long)-PAGE_SIZE
- || (unsigned long)save_str < PAGE_SIZE)
+ if (IS_BAD_PTR(save_ptr))
save_str = BAD_PTR_STRING(save_str);
len = strlen(save_str) + 1;
if (str + len < end)
--
2.16.2