From: Wyatt Feng u32_match_it() executes rule-supplied shift operands on a 32-bit value. A malformed u32 rule can provide a shift count of 32 or more, triggering an undefined shift out-of-bounds during packet evaluation. Validate XT_U32_LEFTSH and XT_U32_RIGHTSH operands in u32_mt_checkentry() and reject malformed rules before they reach the packet path. Fixes: 1b50b8a371e9 ("[NETFILTER]: Add u32 match") Cc: stable@vger.kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Zhengchuan Liang Reported-by: Xin Liu Assisted-by: Codex:GPT-5.4 Signed-off-by: Wyatt Feng Signed-off-by: Ren Wei --- net/netfilter/xt_u32.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/net/netfilter/xt_u32.c b/net/netfilter/xt_u32.c index 117d4615d668..ec1a21e3b6e2 100644 --- a/net/netfilter/xt_u32.c +++ b/net/netfilter/xt_u32.c @@ -100,7 +100,7 @@ static int u32_mt_checkentry(const struct xt_mtchk_param *par) { const struct xt_u32 *data = par->matchinfo; const struct xt_u32_test *ct; - unsigned int i; + unsigned int i, j; if (data->ntests > ARRAY_SIZE(data->tests)) return -EINVAL; @@ -111,6 +111,16 @@ static int u32_mt_checkentry(const struct xt_mtchk_param *par) if (ct->nnums > ARRAY_SIZE(ct->location) || ct->nvalues > ARRAY_SIZE(ct->value)) return -EINVAL; + + for (j = 1; j < ct->nnums; ++j) { + switch (ct->location[j].nextop) { + case XT_U32_LEFTSH: + case XT_U32_RIGHTSH: + if (ct->location[j].number >= 32) + return -EINVAL; + break; + } + } } return 0; -- 2.47.3