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net80211: fix use-after-free in frame defragmentation procedure.

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- Assign frame sequence/fragment number before frame concatenation;
otherwise, frame header pointer (wh) will be invalid.
- Move this code block upper and eliminate duplicate 'lwh = mtod()'
assignment.

Tested with wpi(4) (transmitter) (STA mode) and urtwn(4) (receiver)
(HOSTAP mode).
This commit is contained in:
Andriy Voskoboinyk 2016-05-28 18:49:17 +00:00
parent 7a0c41d5d7
commit 8722deef15
1 changed files with 10 additions and 9 deletions
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19
sys/net80211/ieee80211_input.c
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@ -227,9 +227,16 @@ ieee80211_defrag(struct ieee80211_node *ni, struct mbuf *m, int hdrspace)
lwh = mtod(mfrag, struct ieee80211_frame *);
last_rxseq = le16toh(*(uint16_t *)lwh->i_seq);
/* NB: check seq # and frag together */
if (rxseq != last_rxseq+1 ||
!IEEE80211_ADDR_EQ(wh->i_addr1, lwh->i_addr1) ||
!IEEE80211_ADDR_EQ(wh->i_addr2, lwh->i_addr2)) {
if (rxseq == last_rxseq+1 &&
IEEE80211_ADDR_EQ(wh->i_addr1, lwh->i_addr1) &&
IEEE80211_ADDR_EQ(wh->i_addr2, lwh->i_addr2)) {
/* XXX clear MORE_FRAG bit? */
/* track last seqnum and fragno */
*(uint16_t *) lwh->i_seq = *(uint16_t *) wh->i_seq;
m_adj(m, hdrspace); /* strip header */
m_catpkt(mfrag, m); /* concatenate */
} else {
/*
* Unrelated fragment or no space for it,
* clear current fragments.
@ -247,12 +254,6 @@ ieee80211_defrag(struct ieee80211_node *ni, struct mbuf *m, int hdrspace)
return NULL;
}
mfrag = m;
} else { /* concatenate */
m_adj(m, hdrspace); /* strip header */
m_catpkt(mfrag, m);
/* track last seqnum and fragno */
lwh = mtod(mfrag, struct ieee80211_frame *);
*(uint16_t *) lwh->i_seq = *(uint16_t *) wh->i_seq;
}
if (more_frag) { /* more to come, save */
ni->ni_rxfragstamp = ticks;