From: "Gustavo A. R. Silva" gustavoars@kernel.org
[ Upstream commit 2d3e5caf96b9449af951e63476657acd759c1a30 ]
There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2].
Use an anonymous union with a couple of anonymous structs in order to keep userspace unchanged:
$ pahole -C ip_msfilter net/ipv4/ip_sockglue.o struct ip_msfilter { union { struct { __be32 imsf_multiaddr_aux; /* 0 4 */ __be32 imsf_interface_aux; /* 4 4 */ __u32 imsf_fmode_aux; /* 8 4 */ __u32 imsf_numsrc_aux; /* 12 4 */ __be32 imsf_slist[1]; /* 16 4 */ }; /* 0 20 */ struct { __be32 imsf_multiaddr; /* 0 4 */ __be32 imsf_interface; /* 4 4 */ __u32 imsf_fmode; /* 8 4 */ __u32 imsf_numsrc; /* 12 4 */ __be32 imsf_slist_flex[0]; /* 16 0 */ }; /* 0 16 */ }; /* 0 20 */
/* size: 20, cachelines: 1, members: 1 */ /* last cacheline: 20 bytes */ };
Also, refactor the code accordingly and make use of the struct_size() and flex_array_size() helpers.
This helps with the ongoing efforts to globally enable -Warray-bounds and get us closer to being able to tighten the FORTIFY_SOURCE routines on memcpy().
[1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-an...
Link: https://github.com/KSPP/linux/issues/79 Link: https://github.com/KSPP/linux/issues/109 Signed-off-by: Gustavo A. R. Silva gustavoars@kernel.org Signed-off-by: David S. Miller davem@davemloft.net Stable-dep-of: 5c3be3e0eb44 ("ipmr: fix incorrect parameter validation in the ip_mroute_getsockopt() function") Signed-off-by: Sasha Levin sashal@kernel.org --- include/uapi/linux/in.h | 21 ++++++++++++++++----- net/ipv4/igmp.c | 12 ++++++------ net/ipv4/ip_sockglue.c | 15 ++++++++------- 3 files changed, 30 insertions(+), 18 deletions(-)
diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h index 3960bc3da6b30..066098a5b9360 100644 --- a/include/uapi/linux/in.h +++ b/include/uapi/linux/in.h @@ -190,11 +190,22 @@ struct ip_mreq_source { };
struct ip_msfilter { - __be32 imsf_multiaddr; - __be32 imsf_interface; - __u32 imsf_fmode; - __u32 imsf_numsrc; - __be32 imsf_slist[1]; + union { + struct { + __be32 imsf_multiaddr_aux; + __be32 imsf_interface_aux; + __u32 imsf_fmode_aux; + __u32 imsf_numsrc_aux; + __be32 imsf_slist[1]; + }; + struct { + __be32 imsf_multiaddr; + __be32 imsf_interface; + __u32 imsf_fmode; + __u32 imsf_numsrc; + __be32 imsf_slist_flex[]; + }; + }; };
#define IP_MSFILTER_SIZE(numsrc) \ diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c index cb55fede03c04..134f1682a7e9b 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c @@ -2493,8 +2493,8 @@ int ip_mc_msfilter(struct sock *sk, struct ip_msfilter *msf, int ifindex) goto done; } newpsl->sl_max = newpsl->sl_count = msf->imsf_numsrc; - memcpy(newpsl->sl_addr, msf->imsf_slist, - msf->imsf_numsrc * sizeof(msf->imsf_slist[0])); + memcpy(newpsl->sl_addr, msf->imsf_slist_flex, + flex_array_size(msf, imsf_slist_flex, msf->imsf_numsrc)); err = ip_mc_add_src(in_dev, &msf->imsf_multiaddr, msf->imsf_fmode, newpsl->sl_count, newpsl->sl_addr, 0); if (err) { @@ -2571,14 +2571,14 @@ int ip_mc_msfget(struct sock *sk, struct ip_msfilter *msf, count = psl->sl_count; } copycount = count < msf->imsf_numsrc ? count : msf->imsf_numsrc; - len = copycount * sizeof(psl->sl_addr[0]); + len = flex_array_size(psl, sl_addr, copycount); msf->imsf_numsrc = count; - if (put_user(IP_MSFILTER_SIZE(copycount), optlen) || - copy_to_user(optval, msf, IP_MSFILTER_SIZE(0))) { + if (put_user(struct_size(optval, imsf_slist_flex, copycount), optlen) || + copy_to_user(optval, msf, struct_size(optval, imsf_slist_flex, 0))) { return -EFAULT; } if (len && - copy_to_user(&optval->imsf_slist[0], psl->sl_addr, len)) + copy_to_user(&optval->imsf_slist_flex[0], psl->sl_addr, len)) return -EFAULT; return 0; done: diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index 1b35afd326b8d..2cfc507712300 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -670,12 +670,11 @@ static int set_mcast_msfilter(struct sock *sk, int ifindex, struct sockaddr_storage *group, struct sockaddr_storage *list) { - int msize = IP_MSFILTER_SIZE(numsrc); struct ip_msfilter *msf; struct sockaddr_in *psin; int err, i;
- msf = kmalloc(msize, GFP_KERNEL); + msf = kmalloc(struct_size(msf, imsf_slist_flex, numsrc), GFP_KERNEL); if (!msf) return -ENOBUFS;
@@ -691,7 +690,7 @@ static int set_mcast_msfilter(struct sock *sk, int ifindex,
if (psin->sin_family != AF_INET) goto Eaddrnotavail; - msf->imsf_slist[i] = psin->sin_addr.s_addr; + msf->imsf_slist_flex[i] = psin->sin_addr.s_addr; } err = ip_mc_msfilter(sk, msf, ifindex); kfree(msf); @@ -1236,7 +1235,7 @@ static int do_ip_setsockopt(struct sock *sk, int level, int optname, { struct ip_msfilter *msf;
- if (optlen < IP_MSFILTER_SIZE(0)) + if (optlen < struct_size(msf, imsf_slist_flex, 0)) goto e_inval; if (optlen > READ_ONCE(sysctl_optmem_max)) { err = -ENOBUFS; @@ -1254,7 +1253,8 @@ static int do_ip_setsockopt(struct sock *sk, int level, int optname, err = -ENOBUFS; break; } - if (IP_MSFILTER_SIZE(msf->imsf_numsrc) > optlen) { + if (struct_size(msf, imsf_slist_flex, msf->imsf_numsrc) > + optlen) { kfree(msf); err = -EINVAL; break; @@ -1667,11 +1667,12 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname, { struct ip_msfilter msf;
- if (len < IP_MSFILTER_SIZE(0)) { + if (len < struct_size(&msf, imsf_slist_flex, 0)) { err = -EINVAL; goto out; } - if (copy_from_user(&msf, optval, IP_MSFILTER_SIZE(0))) { + if (copy_from_user(&msf, optval, + struct_size(&msf, imsf_slist_flex, 0))) { err = -EFAULT; goto out; }