[PATCH net-next v2 2/2] ipv4: igmp: convert ip_mc_msfget() to sockopt_t
From: Breno Leitao <leitao@debian.org>
Date: 2026-09-14 12:20:24
Also in:
lkml
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
IP_MSFILTER reads its reply through ip_mc_msfget(), reached from do_ip_getsockopt() and from nowhere else. Convert it, and build the sockopt_t at the call site for as long as the caller still carries a sockptr_t pair. optlen here only has to cover the header, and the real reply size comes from the imsf_numsrc field inside it. This is nasty, but userspace relies on it, so sockopt_expand_out() preserves the same mechanism: it grows optval only for a user address, and assumes the caller left room for the size its own header asked for. The *optlen store moves out of ip_mc_msfget() and into the call site, guarded by !err so the -EINVAL, -ENODEV and -EADDRNOTAVAIL returns still leave the caller's optlen word untouched. The source list also moves from copy_to_sockptr_offset() to a sequential copy_to_iter(). IP_MSFILTER_SIZE(0) and offsetof(struct ip_msfilter, imsf_slist_flex) are both 16, so the bytes land where they did. Signed-off-by: Breno Leitao <leitao@debian.org> --- include/linux/igmp.h | 3 ++- net/ipv4/igmp.c | 23 ++++++++++++++--------- net/ipv4/ip_sockglue.c | 10 +++++++++- 3 files changed, 25 insertions(+), 11 deletions(-)
diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index a0cf0398519fd7..e075611344ef3b 100644
--- a/include/linux/igmp.h
+++ b/include/linux/igmp.h@@ -14,6 +14,7 @@ #include <linux/timer.h> #include <linux/in.h> #include <linux/ip.h> +#include <linux/net.h> #include <linux/refcount.h> #include <linux/sockptr.h> #include <uapi/linux/igmp.h>
@@ -273,7 +274,7 @@ extern int ip_mc_source(int add, int omode, struct sock *sk, struct ip_mreq_source *mreqs, int ifindex); extern int ip_mc_msfilter(struct sock *sk, struct ip_msfilter *msf,int ifindex); extern int ip_mc_msfget(struct sock *sk, struct ip_msfilter *msf, - sockptr_t optval, sockptr_t optlen); + sockopt_t *opt); extern int ip_mc_gsfget(struct sock *sk, struct group_filter *gsf, sockptr_t optval, size_t offset); extern int ip_mc_sf_allow(const struct sock *sk, __be32 local, __be32 rmt,
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index d56355aca79776..144fca158adcb0 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c@@ -2709,8 +2709,8 @@ int ip_mc_msfilter(struct sock *sk, struct ip_msfilter *msf, int ifindex) err = ip_mc_leave_group(sk, &imr); return err; } -int ip_mc_msfget(struct sock *sk, struct ip_msfilter *msf, - sockptr_t optval, sockptr_t optlen) + +int ip_mc_msfget(struct sock *sk, struct ip_msfilter *msf, sockopt_t *opt) { int err, len, count, copycount, msf_size; struct ip_mreqn imr;
@@ -2755,14 +2755,19 @@ int ip_mc_msfget(struct sock *sk, struct ip_msfilter *msf, len = flex_array_size(psl, sl_addr, copycount); msf->imsf_numsrc = count; msf_size = IP_MSFILTER_SIZE(copycount); - if (copy_to_sockptr(optlen, &msf_size, sizeof(int)) || - copy_to_sockptr(optval, msf, IP_MSFILTER_SIZE(0))) { + + /* The source list is sized by the imsf_numsrc the caller left in + * optval, not by optlen, which only has to cover the fixed part. + */ + err = sockopt_expand_out(opt, msf_size); + if (err) + return err; + + opt->optlen = msf_size; + if (copy_to_iter(msf, IP_MSFILTER_SIZE(0), &opt->iter_out) != + IP_MSFILTER_SIZE(0)) return -EFAULT; - } - if (len && - copy_to_sockptr_offset(optval, - offsetof(struct ip_msfilter, imsf_slist_flex), - psl->sl_addr, len)) + if (len && copy_to_iter(psl->sl_addr, len, &opt->iter_out) != len) return -EFAULT; return 0; done:
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index a55ef327ec932c..e06c1f48ecad6e 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c@@ -1706,6 +1706,8 @@ int do_ip_getsockopt(struct sock *sk, int level, int optname, case IP_MSFILTER: { struct ip_msfilter msf; + struct kvec kvec; + sockopt_t opt; if (len < IP_MSFILTER_SIZE(0)) { err = -EINVAL;
@@ -1715,7 +1717,13 @@ int do_ip_getsockopt(struct sock *sk, int level, int optname, err = -EFAULT; goto out; } - err = ip_mc_msfget(sk, &msf, optval, optlen); + err = sockptr_to_sockopt(&opt, optval, optlen, &kvec); + if (err) + goto out; + + err = ip_mc_msfget(sk, &msf, &opt); + if (!err && copy_to_sockptr(optlen, &opt.optlen, sizeof(int))) + err = -EFAULT; goto out; } case MCAST_MSFILTER:
--
2.53.0-Meta