diff options
| author | Cen Zhang (Microsoft) <blbllhy@gmail.com> | 2026-07-23 00:49:55 -0400 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2026-07-28 11:18:58 +0200 |
| commit | aef96eead2860cbfa371e4471d4f04412213b958 (patch) | |
| tree | 3480470d417b31fa210ca15c8074fd1ff1f3fe40 | |
| parent | 295dd295e2137e10e9a5b1891d97e0f08de76f03 (diff) | |
net/sched: cls_u32: validate offshift to prevent shift-out-of-bounds
u32_change() copies the user-provided tc_u32_sel.offshift (unsigned char,
0-255) into the kernel knode object without bounds validation. When a
packet later hits u32_classify() with TC_U32_VAROFFSET set, it evaluates
`ntohs(offmask & *data) >> offshift` where the left operand is a 16-bit
value promoted to a 32-bit int. Any offshift >= 32 is undefined behavior
per C11 6.5.7p3, triggerable by an unprivileged user via user/network
namespaces.
UBSAN: shift-out-of-bounds in net/sched/cls_u32.c:236:43
shift exponent 32 is too large for 32-bit type int
Fix this by rejecting offshift >= 16 during filter creation in
u32_change().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: AutonomousCodeSecurity@microsoft.com
Link: https://lore.kernel.org/all/20260720034514.23053-1-blbllhy@gmail.com
Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Tested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Tested-by: Victor Nogueira <victor@mojatatu.com>
Link: https://patch.msgid.link/20260723044955.89471-1-blbllhy@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
| -rw-r--r-- | net/sched/cls_u32.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index 8f30cc82181d..ac98b1c2144a 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -1107,6 +1107,13 @@ static int u32_change(struct net *net, struct sk_buff *in_skb, goto erridr; } + if (s->offshift >= 16) { + NL_SET_ERR_MSG_MOD(extack, + "offshift must be less than 16"); + err = -EINVAL; + goto erridr; + } + n = kzalloc_flex(*n, sel.keys, s->nkeys); if (n == NULL) { err = -ENOBUFS; |