diff options
| author | Arnaud Lecomte <contact@arnaud-lcm.com> | 2025-04-08 17:55:08 +0200 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2025-04-10 11:24:17 +0200 |
| commit | aabc6596ffb377c4c9c8f335124b92ea282c9821 (patch) | |
| tree | 0df3815864550ee761833803c164491539b78f14 /drivers | |
| parent | 0bb2f7a1ad1f11d861f58e5ee5051c8974ff9569 (diff) | |
net: ppp: Add bound checking for skb data on ppp_sync_txmung
Ensure we have enough data in linear buffer from skb before accessing
initial bytes. This prevents potential out-of-bounds accesses
when processing short packets.
When ppp_sync_txmung receives an incoming package with an empty
payload:
(remote) gef⤠p *(struct pppoe_hdr *) (skb->head + skb->network_header)
$18 = {
type = 0x1,
ver = 0x1,
code = 0x0,
sid = 0x2,
length = 0x0,
tag = 0xffff8880371cdb96
}
from the skb struct (trimmed)
tail = 0x16,
end = 0x140,
head = 0xffff88803346f400 "4",
data = 0xffff88803346f416 ":\377",
truesize = 0x380,
len = 0x0,
data_len = 0x0,
mac_len = 0xe,
hdr_len = 0x0,
it is not safe to access data[2].
Reported-by: syzbot+29fc8991b0ecb186cf40@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=29fc8991b0ecb186cf40
Tested-by: syzbot+29fc8991b0ecb186cf40@syzkaller.appspotmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Arnaud Lecomte <contact@arnaud-lcm.com>
Link: https://patch.msgid.link/20250408-bound-checking-ppp_txmung-v2-1-94bb6e1b92d0@arnaud-lcm.com
[pabeni@redhat.com: fixed subj typo]
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/net/ppp/ppp_synctty.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c index 644e99fc3623..9c4932198931 100644 --- a/drivers/net/ppp/ppp_synctty.c +++ b/drivers/net/ppp/ppp_synctty.c @@ -506,6 +506,11 @@ ppp_sync_txmunge(struct syncppp *ap, struct sk_buff *skb) unsigned char *data; int islcp; + /* Ensure we can safely access protocol field and LCP code */ + if (!pskb_may_pull(skb, 3)) { + kfree_skb(skb); + return NULL; + } data = skb->data; proto = get_unaligned_be16(data); |