[PATCH net 9/9] netfilter: xt_connmark: reject invalid shift parameters
From: Florian Westphal <fw@strlen.de>
Date: 2026-07-03 12:57:54
Also in:
netfilter-devel
Subsystem:
netfilter, networking [general], the rest · Maintainers:
Pablo Neira Ayuso, Florian Westphal, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Wyatt Feng <redacted>
Revision 2 of the CONNMARK target accepts user-controlled shift
parameters and applies them to 32-bit mark values in
connmark_tg_shift().
A shift_bits value of 32 or more triggers an undefined-shift bug when
the rule is evaluated. Invalid shift_dir values are also accepted and
silently fall back to the left-shift path.
Reject invalid revision-2 shift parameters in connmark_tg_check() so
malformed rules fail at installation time, before they can reach the
packet path.
Fixes: 472a73e00757 ("netfilter: xt_conntrack: Support bit-shifting for CONNMARK & MARK targets.")
Reported-by: Yuan Tan <redacted>
Reported-by: Zhengchuan Liang <redacted>
Reported-by: Xin Liu <redacted>
Assisted-by: Codex:GPT-5.4
Signed-off-by: Wyatt Feng <redacted>
Reviewed-by: Ren Wei <redacted>
Reviewed-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
net/netfilter/xt_connmark.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/net/netfilter/xt_connmark.c b/net/netfilter/xt_connmark.c
index 4277084de2e7..2cf27f7d59b9 100644
--- a/net/netfilter/xt_connmark.c
+++ b/net/netfilter/xt_connmark.c@@ -112,6 +112,16 @@ static int connmark_tg_check(const struct xt_tgchk_param *par) return ret; } +static int connmark_tg_check_v2(const struct xt_tgchk_param *par) +{ + const struct xt_connmark_tginfo2 *info = par->targinfo; + + if (info->shift_dir > D_SHIFT_RIGHT || info->shift_bits >= 32) + return -EINVAL; + + return connmark_tg_check(par); +} + static void connmark_tg_destroy(const struct xt_tgdtor_param *par) { nf_ct_netns_put(par->net, par->family);
@@ -162,7 +172,7 @@ static struct xt_target connmark_tg_reg[] __read_mostly = { .name = "CONNMARK", .revision = 2, .family = NFPROTO_IPV4, - .checkentry = connmark_tg_check, + .checkentry = connmark_tg_check_v2, .target = connmark_tg_v2, .targetsize = sizeof(struct xt_connmark_tginfo2), .destroy = connmark_tg_destroy,
@@ -183,7 +193,7 @@ static struct xt_target connmark_tg_reg[] __read_mostly = { .name = "CONNMARK", .revision = 2, .family = NFPROTO_IPV6, - .checkentry = connmark_tg_check, + .checkentry = connmark_tg_check_v2, .target = connmark_tg_v2, .targetsize = sizeof(struct xt_connmark_tginfo2), .destroy = connmark_tg_destroy,
--
2.54.0