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| author | Sanghyun Park <sanghyun.park.cnu@gmail.com> | 2026-09-18 12:26:58 +0900 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-09-23 19:29:26 -0700 |
| commit | 481506a756dcd828ef42391cb08f38d8d96d38fc (patch) | |
| tree | ae5c4c0dc6c7418c29a08919dbf7bcf6c6ce97ed /drivers | |
| parent | 0f2fd31f63c65c409bd336af3a42d478a9207c1f (diff) | |
| download | linux-481506a756dcd828ef42391cb08f38d8d96d38fc.tar.gz linux-481506a756dcd828ef42391cb08f38d8d96d38fc.zip | |
vxlan: use one headroom snapshot for neighbour replies
vxlan_na_create() samples LL_RESERVED_SPACE() to size the reply skb and then
samples it again to reserve headroom. A concurrent vxlan_changelink() can
update needed_headroom between the two reads, creating a TOCTOU race. The
second value can exceed the allocation and make the Ethernet header write out
of bounds.
The race is reproducible on the unpatched kernel. It occurred when
vxlan_na_create() generated a neighbour reply while vxlan_changelink() changed
the link headroom. KASAN caught a four-byte write two bytes beyond a 704-byte
skbuff_small_head allocation.
Snapshot the headroom once and use that value for both allocation and
reservation.
Fixes: 4b29dba9c085 ("vxlan: fix nonfunctional neigh_reduce()")
Signed-off-by: Sanghyun Park <sanghyun.park.cnu@gmail.com>
Link: https://patch.msgid.link/20260918032842.502409-2-sanghyun.park.cnu@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/net/vxlan/vxlan_core.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c index c1d54339fa2b..3390e341d1e5 100644 --- a/drivers/net/vxlan/vxlan_core.c +++ b/drivers/net/vxlan/vxlan_core.c @@ -1958,13 +1958,15 @@ static struct sk_buff *vxlan_na_create(struct sk_buff *request, struct ipv6hdr *pip6; u8 *daddr; int na_olen = 8; /* opt hdr + ETH_ALEN for target */ + int headroom; int ns_olen; int i, len; if (dev == NULL || !pskb_may_pull(request, request->len)) return NULL; - len = LL_RESERVED_SPACE(dev) + sizeof(struct ipv6hdr) + + headroom = LL_RESERVED_SPACE(dev); + len = headroom + sizeof(struct ipv6hdr) + sizeof(*na) + na_olen + dev->needed_tailroom; reply = alloc_skb(len, GFP_ATOMIC); if (reply == NULL) @@ -1972,7 +1974,7 @@ static struct sk_buff *vxlan_na_create(struct sk_buff *request, reply->protocol = htons(ETH_P_IPV6); reply->dev = dev; - skb_reserve(reply, LL_RESERVED_SPACE(request->dev)); + skb_reserve(reply, headroom); skb_push(reply, sizeof(struct ethhdr)); skb_reset_mac_header(reply); |