kernel/include/net/netlink.h, branch linux-5.2.y

netlink: Fix nlmsg_parse as a wrapper for strict message parsing

2019-08-25T14:10:39Z

[ Upstream commit d00ee64e1dcf09b3afefd1340f3e9eb637272714 ] Eric reported a syzbot warning: BUG: KMSAN: uninit-value in nh_valid_get_del_req+0x6f1/0x8c0 net/ipv4/nexthop.c:1510 CPU: 0 PID: 11812 Comm: syz-executor444 Not tainted 5.3.0-rc3+ #17 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x191/0x1f0 lib/dump_stack.c:113 kmsan_report+0x162/0x2d0 mm/kmsan/kmsan_report.c:109 __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:294 nh_valid_get_del_req+0x6f1/0x8c0 net/ipv4/nexthop.c:1510 rtm_del_nexthop+0x1b1/0x610 net/ipv4/nexthop.c:1543 rtnetlink_rcv_msg+0x115a/0x1580 net/core/rtnetlink.c:5223 netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2477 rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:5241 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline] netlink_unicast+0xf6c/0x1050 net/netlink/af_netlink.c:1328 netlink_sendmsg+0x110f/0x1330 net/netlink/af_netlink.c:1917 sock_sendmsg_nosec net/socket.c:637 [inline] sock_sendmsg net/socket.c:657 [inline] ___sys_sendmsg+0x14ff/0x1590 net/socket.c:2311 __sys_sendmmsg+0x53a/0xae0 net/socket.c:2413 __do_sys_sendmmsg net/socket.c:2442 [inline] __se_sys_sendmmsg+0xbd/0xe0 net/socket.c:2439 __x64_sys_sendmmsg+0x56/0x70 net/socket.c:2439 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x63/0xe7 The root cause is nlmsg_parse calling __nla_parse which means the header struct size is not checked. nlmsg_parse should be a wrapper around __nlmsg_parse with NL_VALIDATE_STRICT for the validate argument very much like nlmsg_parse_deprecated is for NL_VALIDATE_LIBERAL. Fixes: 3de6440354465 ("netlink: re-add parse/validate functions in strict mode") Reported-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David Ahern Reviewed-by: Eric Dumazet Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

netlink: add validation of NLA_F_NESTED flag

2019-05-04T05:27:11Z

Add new validation flag NL_VALIDATE_NESTED which adds three consistency checks of NLA_F_NESTED_FLAG: - the flag is set on attributes with NLA_NESTED{,_ARRAY} policy - the flag is not set on attributes with other policies except NLA_UNSPEC - the flag is set on attribute passed to nla_parse_nested() Signed-off-by: Michal Kubecek v2: change error messages to mention NLA_F_NESTED explicitly Reviewed-by: Johannes Berg Reviewed-by: David Ahern Signed-off-by: David S. Miller

netlink: add strict parsing for future attributes

2019-04-27T21:07:22Z

Unfortunately, we cannot add strict parsing for all attributes, as that would break existing userspace. We currently warn about it, but that's about all we can do. For new attributes, however, the story is better: nobody is using them, so we can reject bad sizes. Also, for new attributes, we need not accept them when the policy doesn't declare their usage. David Ahern and I went back and forth on how to best encode this, and the best way we found was to have a "boundary type", from which point on new attributes have all possible validation applied, and NLA_UNSPEC is rejected. As we didn't want to add another argument to all functions that get a netlink policy, the workaround is to encode that boundary in the first entry of the policy array (which is for type 0 and thus probably not really valid anyway). I put it into the validation union for the rare possibility that somebody is actually using attribute 0, which would continue to work fine unless they tried to use the extended validation, which isn't likely. We also didn't find any in-tree users with type 0. The reason for setting the "start strict here" attribute is that we never really need to start strict from 0, which is invalid anyway (or in legacy families where that isn't true, it cannot be set to strict), so we can thus reserve the value 0 for "don't do this check" and don't have to add the tag to all policies right now. Thus, policies can now opt in to this validation, which we should do for all existing policies, at least when adding new attributes. Note that entirely *new* policies won't need to set it, as the use of that should be using nla_parse()/nlmsg_parse() etc. which anyway do fully strict validation now, regardless of this. So in effect, this patch only covers the "existing command with new attribute" case. Signed-off-by: Johannes Berg Signed-off-by: David S. Miller

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

2019-04-27T21:07:22Z

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

2019-04-27T21:07:21Z

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

netlink: add NLA_MIN_LEN

2019-04-27T21:07:21Z

Rather than using NLA_UNSPEC for this type of thing, use NLA_MIN_LEN so we can make NLA_UNSPEC be NLA_REJECT under certain conditions for future attributes. While at it, also use NLA_EXACT_LEN for the struct example. Signed-off-by: Johannes Berg Signed-off-by: David S. Miller

netlink: make nla_nest_start() add NLA_F_NESTED flag

2019-04-27T21:03:44Z

Even if the NLA_F_NESTED flag was introduced more than 11 years ago, most netlink based interfaces (including recently added ones) are still not setting it in kernel generated messages. Without the flag, message parsers not aware of attribute semantics (e.g. wireshark dissector or libmnl's mnl_nlmsg_fprintf()) cannot recognize nested attributes and won't display the structure of their contents. Unfortunately we cannot just add the flag everywhere as there may be userspace applications which check nlattr::nla_type directly rather than through a helper masking out the flags. Therefore the patch renames nla_nest_start() to nla_nest_start_noflag() and introduces nla_nest_start() as a wrapper adding NLA_F_NESTED. The calls which add NLA_F_NESTED manually are rewritten to use nla_nest_start(). Except for changes in include/net/netlink.h, the patch was generated using this semantic patch: @@ expression E1, E2; @@ -nla_nest_start(E1, E2) +nla_nest_start_noflag(E1, E2) @@ expression E1, E2; @@ -nla_nest_start_noflag(E1, E2 | NLA_F_NESTED) +nla_nest_start(E1, E2) Signed-off-by: Michal Kubecek Acked-by: Jiri Pirko Acked-by: David Ahern Signed-off-by: David S. Miller

netlink: reduce NLA_POLICY_NESTED{,_ARRAY} arguments

2019-02-01T10:06:55Z

In typical cases, there's no need to pass both the maxattr and the policy array pointer, as the maxattr should just be ARRAY_SIZE(policy) - 1. Therefore, to be less error prone, just remove the maxattr argument from the default macros and deduce the size accordingly. Leave the original macros with a leading underscore to use here and in case somebody needs to pass a policy pointer where the policy isn't declared in the same place and thus ARRAY_SIZE() cannot be used. Signed-off-by: Johannes Berg

netlink: replace __NLA_ENSURE implementation

2018-10-12T18:00:22Z

We already have BUILD_BUG_ON_ZERO() which I just hadn't found before, so we should use it here instead of open-coding another implementation thereof. Signed-off-by: Johannes Berg Signed-off-by: David S. Miller

netlink: Add strict version of nlmsg_parse and nla_parse

2018-10-08T17:39:04Z

nla_parse is currently lenient on message parsing, allowing type to be 0 or greater than max expected and only logging a message "netlink: %d bytes leftover after parsing attributes in process `%s'." if the netlink message has unknown data at the end after parsing. What this could mean is that the header at the front of the attributes is actually wrong and the parsing is shifted from what is expected. Add a new strict version that actually fails with EINVAL if there are any bytes remaining after the parsing loop completes, if the atttrbitue type is 0 or greater than max expected. Signed-off-by: David Ahern Acked-by: Christian Brauner Signed-off-by: David S. Miller