| Message ID | 20210731170830.GA48844@embeddedor (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 2d3e5caf96b9449af951e63476657acd759c1a30 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [next] net/ipv4: Replace one-element array with flexible-array member | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Guessed tree name to be net-next |
| netdev/subject_prefix | warning | Target tree name not specified in the subject |
| netdev/cc_maintainers | success | CCed 5 of 5 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 5127 this patch: 5127 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | warning | WARNING: line length of 81 exceeds 80 columns |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 5188 this patch: 5188 |
| netdev/header_inline | success | Link |
On 8/2/21 09:20, patchwork-bot+netdevbpf@kernel.org wrote: > Hello: > > This patch was applied to netdev/net-next.git (refs/heads/master): > > On Sat, 31 Jul 2021 12:08:30 -0500 you wrote: >> 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: >> >> [...] > > Here is the summary with links: > - [next] net/ipv4: Replace one-element array with flexible-array member > https://git.kernel.org/netdev/net-next/c/2d3e5caf96b9 arghh... this has a bug. Sorry, Dave. I will send a fix for this, shortly. -- Gustavo
On 8/2/21 13:46, Gustavo A. R. Silva wrote: > > > On 8/2/21 09:20, patchwork-bot+netdevbpf@kernel.org wrote: >> Hello: >> >> This patch was applied to netdev/net-next.git (refs/heads/master): >> >> On Sat, 31 Jul 2021 12:08:30 -0500 you wrote: >>> 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: >>> >>> [...] >> >> Here is the summary with links: >> - [next] net/ipv4: Replace one-element array with flexible-array member >> https://git.kernel.org/netdev/net-next/c/2d3e5caf96b9 > > arghh... this has a bug. Sorry, Dave. I will send a fix for this, shortly. > BTW... can we expect msf->imsf_numsrc to be zero at some point in the following pieces of code? net/ipv4/igmp.c: 2553 copycount = count < msf->imsf_numsrc ? count : msf->imsf_numsrc; 2554 len = copycount * sizeof(psl->sl_addr[0]); 2555 msf->imsf_numsrc = count; 2556 if (put_user(IP_MSFILTER_SIZE(copycount), optlen) || 2557 copy_to_user(optval, msf, IP_MSFILTER_SIZE(0))) { 2558 return -EFAULT; 2559 } net/ipv4/ip_sockglue.c: 1228 case IP_MSFILTER: 1229 { 1230 struct ip_msfilter *msf; 1231 1232 if (optlen < IP_MSFILTER_SIZE(0)) 1233 goto e_inval; 1234 if (optlen > sysctl_optmem_max) { 1235 err = -ENOBUFS; 1236 break; 1237 } 1238 msf = memdup_sockptr(optval, optlen); 1239 if (IS_ERR(msf)) { ... 1250 if (IP_MSFILTER_SIZE(msf->imsf_numsrc) > optlen) { 1251 kfree(msf); 1252 err = -EINVAL; 1253 break; 1254 } 1255 err = ip_mc_msfilter(sk, msf, 0); 1256 kfree(msf); 1257 break; 1258 } Thanks -- Gustavo
diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h index d1b327036ae4..193b7cf1f0ac 100644 --- a/include/uapi/linux/in.h +++ b/include/uapi/linux/in.h @@ -188,11 +188,22 @@ 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 03589a04f9aa..a5f4ecb02e97 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c @@ -2475,8 +2475,8 @@ 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) { @@ -2551,14 +2551,14 @@ 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 ec6036713e2c..bbe660b84a91 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -663,12 +663,11 @@ 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; @@ -684,7 +683,7 @@ 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); @@ -1229,7 +1228,7 @@ 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 > sysctl_optmem_max) { err = -ENOBUFS; @@ -1247,7 +1246,8 @@ 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; @@ -1660,11 +1660,12 @@ 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; }
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-and-one-element-arrays 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> --- include/uapi/linux/in.h | 21 ++++++++++++++++----- net/ipv4/igmp.c | 12 ++++++------ net/ipv4/ip_sockglue.c | 15 ++++++++------- 3 files changed, 30 insertions(+), 18 deletions(-)