kernel/linux.git/include/net/genetlink.h, branch v5.8.17

genetlink: remove genl_bind

2020-07-01T22:49:11+00:00

A potential deadlock can occur during registering or unregistering a new generic netlink family between the main nl_table_lock and the cb_lock where each thread wants the lock held by the other, as demonstrated below. 1) Thread 1 is performing a netlink_bind() operation on a socket. As part of this call, it will call netlink_lock_table(), incrementing the nl_table_users count to 1. 2) Thread 2 is registering (or unregistering) a genl_family via the genl_(un)register_family() API. The cb_lock semaphore will be taken for writing. 3) Thread 1 will call genl_bind() as part of the bind operation to handle subscribing to GENL multicast groups at the request of the user. It will attempt to take the cb_lock semaphore for reading, but it will fail and be scheduled away, waiting for Thread 2 to finish the write. 4) Thread 2 will call netlink_table_grab() during the (un)registration call. However, as Thread 1 has incremented nl_table_users, it will not be able to proceed, and both threads will be stuck waiting for the other. genl_bind() is a noop, unless a genl_family implements the mcast_bind() function to handle setting up family-specific multicast operations. Since no one in-tree uses this functionality as Cong pointed out, simply removing the genl_bind() function will remove the possibility for deadlock, as there is no attempt by Thread 1 above to take the cb_lock semaphore. Fixes: c380d9a7afff ("genetlink: pass multicast bind/unbind to families") Suggested-by: Cong Wang Acked-by: Johannes Berg Reported-by: kernel test robot Signed-off-by: Sean Tranchetti Signed-off-by: David S. Miller

genetlink: get rid of family->attrbuf

2020-06-30T00:15:57+00:00

genl_family_rcv_msg_attrs_parse() reuses the global family->attrbuf when family->parallel_ops is false. However, family->attrbuf is not protected by any lock on the genl_family_rcv_msg_doit() code path. This leads to several different consequences, one of them is UAF, like the following: genl_family_rcv_msg_doit(): genl_start(): genl_family_rcv_msg_attrs_parse() attrbuf = family->attrbuf __nlmsg_parse(attrbuf); genl_family_rcv_msg_attrs_parse() attrbuf = family->attrbuf __nlmsg_parse(attrbuf); info->attrs = attrs; cb->data = info; netlink_unicast_kernel(): consume_skb() genl_lock_dumpit(): genl_dumpit_info(cb)->attrs Note family->attrbuf is an array of pointers to the skb data, once the skb is freed, any dereference of family->attrbuf will be a UAF. Maybe we could serialize the family->attrbuf with genl_mutex too, but that would make the locking more complicated. Instead, we can just get rid of family->attrbuf and always allocate attrbuf from heap like the family->parallel_ops==true code path. This may add some performance overhead but comparing with taking the global genl_mutex, it still looks better. Fixes: 75cdbdd08900 ("net: ieee802154: have genetlink code to parse the attrs during dumpit") Fixes: 057af7071344 ("net: tipc: have genetlink code to parse the attrs during dumpit") Reported-and-tested-by: syzbot+3039ddf6d7b13daf3787@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+80cad1e3cb4c41cde6ff@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+736bcbcb11b60d0c0792@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+520f8704db2b68091d44@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+c96e4dfb32f8987fdeed@syzkaller.appspotmail.com Cc: Jiri Pirko Signed-off-by: Cong Wang Signed-off-by: David S. Miller

net: genetlink: remove unused genl_family_attrbuf()

2019-10-06T13:44:47+00:00

genl_family_attrbuf() function is no longer used by anyone, so remove it. Signed-off-by: Jiri Pirko Signed-off-by: David S. Miller

net: genetlink: parse attrs and store in contect info struct during dumpit

2019-10-06T13:44:47+00:00

Extend the dumpit info struct for attrs. Instead of existing attribute validation do parse them and save in the info struct. Caller can benefit from this and does not have to do parse itself. In order to properly free attrs, genl_family pointer needs to be added to dumpit info struct as well. Signed-off-by: Jiri Pirko Signed-off-by: David S. Miller

net: genetlink: introduce dump info struct to be available during dumpit op

2019-10-06T13:44:46+00:00

Currently the cb->data is taken by ops during non-parallel dumping. Introduce a new structure genl_dumpit_info and store the ops there. Distribute the info to both non-parallel and parallel dumping. Also add a helper genl_dumpit_info() to easily get the info structure in the dumpit callback from cb. Signed-off-by: Jiri Pirko Signed-off-by: David S. Miller

genetlink: optionally validate strictly/dumps

2019-04-27T21:07:22+00:00

Add options to strictly validate messages and dump messages, sometimes perhaps validating dump messages non-strictly may be required, so add an option for that as well. Since none of this can really be applied to existing commands, set the options everwhere using the following spatch: @@ identifier ops; expression X; @@ struct genl_ops ops[] = { ..., { .cmd = X, + .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP, ... }, ... }; For new commands one should just not copy the .validate 'opt-out' flags and thus get strict validation. Signed-off-by: Johannes Berg Signed-off-by: David S. Miller

netlink: re-add parse/validate functions in strict mode

2019-04-27T21:07:22+00:00

This re-adds the parse and validate functions like nla_parse() that are now actually strict after the previous rename and were just split out to make sure everything is converted (and if not compilation of the previous patch would fail.) Signed-off-by: Johannes Berg Signed-off-by: David S. Miller

netlink: make validation more configurable for future strictness

2019-04-27T21:07:21+00:00

We currently have two levels of strict validation: 1) liberal (default) - undefined (type >= max) & NLA_UNSPEC attributes accepted - attribute length >= expected accepted - garbage at end of message accepted 2) strict (opt-in) - NLA_UNSPEC attributes accepted - attribute length >= expected accepted Split out parsing strictness into four different options: * TRAILING - check that there's no trailing data after parsing attributes (in message or nested) * MAXTYPE - reject attrs > max known type * UNSPEC - reject attributes with NLA_UNSPEC policy entries * STRICT_ATTRS - strictly validate attribute size The default for future things should be *everything*. The current *_strict() is a combination of TRAILING and MAXTYPE, and is renamed to _deprecated_strict(). The current regular parsing has none of this, and is renamed to *_parse_deprecated(). Additionally it allows us to selectively set one of the new flags even on old policies. Notably, the UNSPEC flag could be useful in this case, since it can be arranged (by filling in the policy) to not be an incompatible userspace ABI change, but would then going forward prevent forgetting attribute entries. Similar can apply to the POLICY flag. We end up with the following renames: * nla_parse -> nla_parse_deprecated * nla_parse_strict -> nla_parse_deprecated_strict * nlmsg_parse -> nlmsg_parse_deprecated * nlmsg_parse_strict -> nlmsg_parse_deprecated_strict * nla_parse_nested -> nla_parse_nested_deprecated * nla_validate_nested -> nla_validate_nested_deprecated Using spatch, of course: @@ expression TB, MAX, HEAD, LEN, POL, EXT; @@ -nla_parse(TB, MAX, HEAD, LEN, POL, EXT) +nla_parse_deprecated(TB, MAX, HEAD, LEN, POL, EXT) @@ expression NLH, HDRLEN, TB, MAX, POL, EXT; @@ -nlmsg_parse(NLH, HDRLEN, TB, MAX, POL, EXT) +nlmsg_parse_deprecated(NLH, HDRLEN, TB, MAX, POL, EXT) @@ expression NLH, HDRLEN, TB, MAX, POL, EXT; @@ -nlmsg_parse_strict(NLH, HDRLEN, TB, MAX, POL, EXT) +nlmsg_parse_deprecated_strict(NLH, HDRLEN, TB, MAX, POL, EXT) @@ expression TB, MAX, NLA, POL, EXT; @@ -nla_parse_nested(TB, MAX, NLA, POL, EXT) +nla_parse_nested_deprecated(TB, MAX, NLA, POL, EXT) @@ expression START, MAX, POL, EXT; @@ -nla_validate_nested(START, MAX, POL, EXT) +nla_validate_nested_deprecated(START, MAX, POL, EXT) @@ expression NLH, HDRLEN, MAX, POL, EXT; @@ -nlmsg_validate(NLH, HDRLEN, MAX, POL, EXT) +nlmsg_validate_deprecated(NLH, HDRLEN, MAX, POL, EXT) For this patch, don't actually add the strict, non-renamed versions yet so that it breaks compile if I get it wrong. Also, while at it, make nla_validate and nla_parse go down to a common __nla_validate_parse() function to avoid code duplication. Ultimately, this allows us to have very strict validation for every new caller of nla_parse()/nlmsg_parse() etc as re-introduced in the next patch, while existing things will continue to work as is. In effect then, this adds fully strict validation for any new command. Signed-off-by: Johannes Berg Signed-off-by: David S. Miller

genetlink: make policy common to family

2019-03-22T14:38:23+00:00

Since maxattr is common, the policy can't really differ sanely, so make it common as well. The only user that did in fact manage to make a non-common policy is taskstats, which has to be really careful about it (since it's still using a common maxattr!). This is no longer supported, but we can fake it using pre_doit. This reduces the size of e.g. nl80211.o (which has lots of commands): text data bss dec hex filename 398745 14323 2240 415308 6564c net/wireless/nl80211.o (before) 397913 14331 2240 414484 65314 net/wireless/nl80211.o (after) -------------------------------- -832 +8 0 -824 Which is obviously just 8 bytes for each command, and an added 8 bytes for the new policy pointer. I'm not sure why the ops list is counted as .text though. Most of the code transformations were done using the following spatch: @ops@ identifier OPS; expression POLICY; @@ struct genl_ops OPS[] = { ..., { - .policy = POLICY, }, ... }; @@ identifier ops.OPS; expression ops.POLICY; identifier fam; expression M; @@ struct genl_family fam = { .ops = OPS, .maxattr = M, + .policy = POLICY, ... }; This also gets rid of devlink_nl_cmd_region_read_dumpit() accessing the cb->data as ops, which we want to change in a later genl patch. Signed-off-by: Johannes Berg Signed-off-by: David S. Miller

genetlink: constify genl_err_attr() argument

2018-08-30T02:42:52+00:00

genl_err_attr() sets netlink_ext_ack::bad_attr which is a pointer to const struct nlattr so make the attr argument also const. Signed-off-by: Michal Kubecek Signed-off-by: David S. Miller