diff options
| author | Eric Dumazet <edumazet@google.com> | 2026-04-30 10:06:11 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-05-02 03:01:40 +0300 |
| commit | 4f34002e2e37639133693c13a2a9977fab86880d (patch) | |
| tree | 687078f25a5346c6d83292cd034b5e99418f9f01 | |
| parent | f93836b236773862e9ee268a82e3614caf77ea01 (diff) | |
| download | linux-4f34002e2e37639133693c13a2a9977fab86880d.tar.xz | |
ipmr: prevent info-leak in pmr_cache_report()
Yiming Qian reported:
<quote>
ipmr_cache_report()` allocates a report skb with `alloc_skb(128,
GFP_ATOMIC)` and appends a `struct igmphdr` using `skb_put()`. In the
non-`IGMPMSG_WHOLEPKT` path it initializes only:
- `igmp->type`
- `igmp->code`
but does not initialize:
- `igmp->csum`
- `igmp->group`
Later, `igmpmsg_netlink_event()` copies the bytes after `sizeof(struct
igmpmsg)` into the `IPMRA_CREPORT_PKT` netlink attribute and emits
`RTM_NEWCACHEREPORT` on `RTNLGRP_IPV4_MROUTE_R`.
As a result, 6 bytes of stale heap data from the skb head are
disclosed to userspace.
</quote>
Let's use skb_put_zero() instead of skb_put() to fix this bug.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Yiming Qian <yimingqian591@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260430070611.4004529-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/ipv4/ipmr.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c index 2058ca860294..05fb6eefe0be 100644 --- a/net/ipv4/ipmr.c +++ b/net/ipv4/ipmr.c @@ -1112,11 +1112,12 @@ static int ipmr_cache_report(const struct mr_table *mrt, msg->im_vif_hi = vifi >> 8; ipv4_pktinfo_prepare(mroute_sk, pkt, false); memcpy(skb->cb, pkt->cb, sizeof(skb->cb)); - /* Add our header */ - igmp = skb_put(skb, sizeof(struct igmphdr)); + /* Add our header. + * Note that code, csum and group fields are cleared. + */ + igmp = skb_put_zero(skb, sizeof(struct igmphdr)); igmp->type = assert; msg->im_msgtype = assert; - igmp->code = 0; ip_hdr(skb)->tot_len = htons(skb->len); /* Fix the length */ skb->transport_header = skb->network_header; } |