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blob: add a magic offset to nesting cookies to ensure that NULL is never returned as a normal value

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Signed-off-by: Felix Fietkau <nbd@openwrt.org>
This commit is contained in:
Felix Fietkau 2013-10-16 01:22:02 +02:00
parent e9fb256ca5
commit 458c3937bc
3 changed files with 7 additions and 5 deletions
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6
blob.c
View file

@ -40,14 +40,14 @@ blob_init(struct blob_attr *attr, int id, unsigned int len)
static inline struct blob_attr *
offset_to_attr(struct blob_buf *buf, int offset)
{
void *ptr = (char *)buf->buf + offset;
void *ptr = (char *)buf->buf + offset - BLOB_COOKIE;
return ptr;
}
static inline int
attr_to_offset(struct blob_buf *buf, struct blob_attr *attr)
{
return (char *)attr - (char *) buf->buf;
return (char *)attr - (char *) buf->buf + BLOB_COOKIE;
}
void
@ -65,7 +65,7 @@ static struct blob_attr *
blob_add(struct blob_buf *buf, struct blob_attr *pos, int id, int payload)
{
int offset = attr_to_offset(buf, pos);
int required = (offset + sizeof(struct blob_attr) + payload) - buf->buflen;
int required = (offset - BLOB_COOKIE + sizeof(struct blob_attr) + payload) - buf->buflen;
struct blob_attr *attr;
if (required > 0) {

2
blob.h
View file

@ -28,6 +28,8 @@
#include "utils.h"
#define BLOB_COOKIE 0x01234567
enum {
BLOB_ATTR_UNSPEC,
BLOB_ATTR_NESTED,

4
blobmsg.c
View file

@ -195,7 +195,7 @@ blobmsg_new(struct blob_buf *buf, int type, const char *name, int payload_len, v
static inline int
attr_to_offset(struct blob_buf *buf, struct blob_attr *attr)
{
return (char *)attr - (char *) buf->buf;
return (char *)attr - (char *) buf->buf + BLOB_COOKIE;
}
@ -262,7 +262,7 @@ void *
blobmsg_realloc_string_buffer(struct blob_buf *buf, int maxlen)
{
struct blob_attr *attr = blob_next(buf->head);
int offset = attr_to_offset(buf, blob_next(buf->head)) + blob_pad_len(attr);
int offset = attr_to_offset(buf, blob_next(buf->head)) + blob_pad_len(attr) - BLOB_COOKIE;
int required = maxlen - (buf->buflen - offset);
if (required <= 0)