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pppd: Add checks to avoid out-of-bounds writes to static data #589

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Merged
paulusmack merged 1 commit into from
May 25, 2026
Merged

pppd: Add checks to avoid out-of-bounds writes to static data #589

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7 changes: 4 additions & 3 deletions pppd/fsm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -762,12 +762,13 @@ void
fsm_sdata(fsm *f, int code, int id, u_char *data, int datalen)
{
u_char *outp;
int outlen;
int outlen, mtu;

/* Adjust length to be smaller than MTU */
outp = outpacket_buf;
if (datalen > peer_mru[f->unit] - HEADERLEN)
datalen = peer_mru[f->unit] - HEADERLEN;
mtu = MIN(peer_mru[f->unit], PPP_MRU) - HEADERLEN;
if (datalen > mtu)
datalen = mtu;
if (datalen && data != outp + PPP_HDRLEN + HEADERLEN)
BCOPY(data, outp + PPP_HDRLEN + HEADERLEN, datalen);
outlen = datalen + HEADERLEN;
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5 changes: 3 additions & 2 deletions pppd/ipcp.c
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Expand Up @@ -1709,13 +1709,14 @@ ipcp_reqci(fsm *f, u_char *inp, int *len, int reject_if_disagree)
/*
* If we aren't rejecting this packet, and we want to negotiate
* their address, and they didn't send their address, then we
* send a NAK with a CI_ADDR option appended. We assume the
* send a NAK with a CI_ADDR option appended. We check that the
* input buffer is long enough that we can append the extra
* option safely.
*/
if (rc != CONFREJ && !ho->neg_addr && !ho->old_addrs &&
wo->req_addr && !reject_if_disagree &&
((wo->hisaddr && !wo->accept_remote) || !noremoteip)) {
((wo->hisaddr && !wo->accept_remote) || !noremoteip) &&
(rc == CONFACK || ucp + CILEN_ADDR <= inp + PPP_MRU - HEADERLEN)) {
if (rc == CONFACK) {
rc = CONFNAK;
ucp = inp; /* reset pointer */
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