[DPDK/other Bug 2005] GTP ptype parser out-of-bounds read

[DPDK/other Bug 2005] GTP ptype parser out-of-bounds read

[bugzilla]

https://bugs.dpdk.org/show_bug.cgi?id=2005

            Bug ID: 2005
           Summary: GTP ptype parser out-of-bounds read
           Product: DPDK
           Version: unspecified
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: other
          Assignee: dev@dpdk.org
          Reporter: thomas@monjalon.net
  Target Milestone: ---
             Group: security

Report date: 2026-06-02
Reported by: Borys Tsyrulnikov <tsyrulnikov.borys@gmail.com>

Hello DPDK security team,

I'm reporting two memory-safety defects found by source audit of the
development branch (HEAD a53fd23, == origin/main at time of writing). One is
reproducible with an AddressSanitizer PoC; the other is source-verified. Fixes
for both are included inline below and attached as patches.

Credit: please credit me as "Borys Tsyrulnikov".
Embargo: No specific embargo requested from my side; please coordinate
according
to the DPDK process if the issues qualify. I will not disclose publicly (PoC or
details) until you advise.


================================================================
Issue 1 — lib/net: out-of-bounds read in GTP packet-type parsing
================================================================
Severity: medium (remote DoS on hosts running the software ptype parser on
untrusted traffic). REPRODUCIBLE — AddressSanitizer PoC attached.

Location: lib/net/rte_net.c:235, function ptype_tunnel_with_udp(), GTP case.

Description:
The GTP case reads the inner IP-version byte at offset gtp_len (8, or 12 when
the E/S/PN flags are set) from the GTP header:

    gh = rte_pktmbuf_read(m, *off, sizeof(*gh), &gh_copy);  /*
validates 8 bytes */
    ...
    if (gh->msg_type == 0xff)
        ip_ver = *(const uint8_t *)((const char *)gh + gtp_len);  /*
reads byte 8 or 12 */

rte_pktmbuf_read() only guarantees sizeof(struct rte_gtp_hdr) == 8 bytes. The
read at gh[gtp_len] is past that, with no further bounds check. When the 8 GTP
bytes are not contiguous in the first mbuf segment, rte_pktmbuf_read() returns
the 8-byte on-stack copy gh_copy, so gh[gtp_len] is an out-of-bounds read past
that stack object.

Reachability / attacker model:
rte_net_get_ptype(m, &lens, RTE_PTYPE_ALL_MASK) runs on received,
attacker-controlled packets — notably lib/vhost/virtio_net.c:2800 (the host
parsing packets from a guest VM), plus virtio/vhost/tap/netvsc RX. A malicious
guest can craft a GTP packet with E/S/PN set and split across mbuf segments to
force the stack-copy path and trigger the over-read.

Reproduction (attached poc_gtp_oob.c + asan_crash.sanitized.txt, against an
ASan
DPDK build):
    READ of size 1 ... ptype_tunnel_with_udp ../lib/net/rte_net.c:235
    [64, 72) 'gh_copy' <== access at offset 76 overflows this variable

Fix (attached patch-02-net-gtp-ptype.patch):
Read the version byte through the bounds-checked accessor and treat a short
packet as unknown inner protocol:

    + const uint8_t *ver;
    ...
    - ip_ver = *(const uint8_t *)((const char *)gh + gtp_len);
    - ip_ver = (ip_ver) & 0xf0;
    + ver = rte_pktmbuf_read(m, *off + gtp_len, sizeof(ip_ver), &ip_ver);
    + ip_ver = (ver == NULL) ? 0 : (*ver & 0xf0);

Patch commit-message tags (for the eventual fix; NOT recipients of this email):
  Fixes: 64ed7f854cf4 ("net: add tunnel packet type parsing")  [in v25.03+]
  Cc: stable@dpdk.org ; regression author Jie Hai <haijie1@huawei.com>

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