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attr: Add padding if nested data does not end at an alignment boundry

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This could happen if a user put an unaligned amount of data inside
an attribute with nlmsg_append().
This commit is contained in:
Thomas Graf 2010-10-29 18:40:48 +02:00
parent cc22992d0c
commit 93f992eac5
1 changed files with 17 additions and 0 deletions
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17
lib/attr.c
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@ -1151,9 +1151,26 @@ struct nlattr *nla_nest_start(struct nl_msg *msg, int attrtype)
*/
int nla_nest_end(struct nl_msg *msg, struct nlattr *start)
{
size_t pad;
start->nla_len = (unsigned char *) nlmsg_tail(msg->nm_nlh) -
(unsigned char *) start;
pad = NLMSG_ALIGN(msg->nm_nlh->nlmsg_len) - msg->nm_nlh->nlmsg_len;
if (pad > 0) {
/*
* Data inside attribute does not end at a alignment boundry.
* Pad accordingly and accoun for the additional space in
* the message. nlmsg_reserve() may never fail in this situation,
* the allocate message buffer must be a multiple of NLMSG_ALIGNTO.
*/
if (!nlmsg_reserve(msg, pad, 0))
BUG();
NL_DBG(2, "msg %p: attr <%p> %d: added %zu bytes of padding\n",
msg, start, start->nla_type, pad);
}
NL_DBG(2, "msg %p: attr <%p> %d: closing nesting, len=%u\n",
msg, start, start->nla_type, start->nla_len);