From: Jamal Hadi Salim jhs@mojatatu.com
[ Upstream commit e68409db995380d1badacba41ff24996bd396171 ]
A match entry is uniquely identified with an "address" or "path" in the form of: hashtable ID(12b):bucketid(8b):nodeid(12b).
When creating table match entries all of hash table id, bucket id and node (match entry id) are needed to be either specified by the user or reasonable in-kernel defaults are used. The in-kernel default for a table id is 0x800(omnipresent root table); for bucketid it is 0x0. Prior to this fix there was none for a nodeid i.e. the code assumed that the user passed the correct nodeid and if the user passes a nodeid of 0 (as Mingi Cho did) then that is what was used. But nodeid of 0 is reserved for identifying the table. This is not a problem until we dump. The dump code notices that the nodeid is zero and assumes it is referencing a table and therefore references table struct tc_u_hnode instead of what was created i.e match entry struct tc_u_knode.
Ming does an equivalent of: tc filter add dev dummy0 parent 10: prio 1 handle 0x1000 \ protocol ip u32 match ip src 10.0.0.1/32 classid 10:1 action ok
Essentially specifying a table id 0, bucketid 1 and nodeid of zero Tableid 0 is remapped to the default of 0x800. Bucketid 1 is ignored and defaults to 0x00. Nodeid was assumed to be what Ming passed - 0x000
dumping before fix shows: ~$ tc filter ls dev dummy0 parent 10: filter protocol ip pref 1 u32 chain 0 filter protocol ip pref 1 u32 chain 0 fh 800: ht divisor 1 filter protocol ip pref 1 u32 chain 0 fh 800: ht divisor -30591
Note that the last line reports a table instead of a match entry (you can tell this because it says "ht divisor..."). As a result of reporting the wrong data type (misinterpretting of struct tc_u_knode as being struct tc_u_hnode) the divisor is reported with value of -30591. Ming identified this as part of the heap address (physmap_base is 0xffff8880 (-30591 - 1)).
The fix is to ensure that when table entry matches are added and no nodeid is specified (i.e nodeid == 0) then we get the next available nodeid from the table's pool.
After the fix, this is what the dump shows: $ tc filter ls dev dummy0 parent 10: filter protocol ip pref 1 u32 chain 0 filter protocol ip pref 1 u32 chain 0 fh 800: ht divisor 1 filter protocol ip pref 1 u32 chain 0 fh 800::800 order 2048 key ht 800 bkt 0 flowid 10:1 not_in_hw match 0a000001/ffffffff at 12 action order 1: gact action pass random type none pass val 0 index 1 ref 1 bind 1
Reported-by: Mingi Cho mgcho.minic@gmail.com Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Jamal Hadi Salim jhs@mojatatu.com Link: https://lore.kernel.org/r/20230726135151.416917-1-jhs@mojatatu.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/cls_u32.c | 56 ++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 50 insertions(+), 6 deletions(-)
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index e5cc2b4d38d5a..316ccbb01b55f 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -1004,18 +1004,62 @@ static int u32_change(struct net *net, struct sk_buff *in_skb, return -EINVAL; }
+ /* At this point, we need to derive the new handle that will be used to + * uniquely map the identity of this table match entry. The + * identity of the entry that we need to construct is 32 bits made of: + * htid(12b):bucketid(8b):node/entryid(12b) + * + * At this point _we have the table(ht)_ in which we will insert this + * entry. We carry the table's id in variable "htid". + * Note that earlier code picked the ht selection either by a) the user + * providing the htid specified via TCA_U32_HASH attribute or b) when + * no such attribute is passed then the root ht, is default to at ID + * 0x[800][00][000]. Rule: the root table has a single bucket with ID 0. + * If OTOH the user passed us the htid, they may also pass a bucketid of + * choice. 0 is fine. For example a user htid is 0x[600][01][000] it is + * indicating hash bucketid of 1. Rule: the entry/node ID _cannot_ be + * passed via the htid, so even if it was non-zero it will be ignored. + * + * We may also have a handle, if the user passed one. The handle also + * carries the same addressing of htid(12b):bucketid(8b):node/entryid(12b). + * Rule: the bucketid on the handle is ignored even if one was passed; + * rather the value on "htid" is always assumed to be the bucketid. + */ if (handle) { + /* Rule: The htid from handle and tableid from htid must match */ if (TC_U32_HTID(handle) && TC_U32_HTID(handle ^ htid)) { NL_SET_ERR_MSG_MOD(extack, "Handle specified hash table address mismatch"); return -EINVAL; } - handle = htid | TC_U32_NODE(handle); - err = idr_alloc_u32(&ht->handle_idr, NULL, &handle, handle, - GFP_KERNEL); - if (err) - return err; - } else + /* Ok, so far we have a valid htid(12b):bucketid(8b) but we + * need to finalize the table entry identification with the last + * part - the node/entryid(12b)). Rule: Nodeid _cannot be 0_ for + * entries. Rule: nodeid of 0 is reserved only for tables(see + * earlier code which processes TC_U32_DIVISOR attribute). + * Rule: The nodeid can only be derived from the handle (and not + * htid). + * Rule: if the handle specified zero for the node id example + * 0x60000000, then pick a new nodeid from the pool of IDs + * this hash table has been allocating from. + * If OTOH it is specified (i.e for example the user passed a + * handle such as 0x60000123), then we use it generate our final + * handle which is used to uniquely identify the match entry. + */ + if (!TC_U32_NODE(handle)) { + handle = gen_new_kid(ht, htid); + } else { + handle = htid | TC_U32_NODE(handle); + err = idr_alloc_u32(&ht->handle_idr, NULL, &handle, + handle, GFP_KERNEL); + if (err) + return err; + } + } else { + /* The user did not give us a handle; lets just generate one + * from the table's pool of nodeids. + */ handle = gen_new_kid(ht, htid); + }
if (tb[TCA_U32_SEL] == NULL) { NL_SET_ERR_MSG_MOD(extack, "Selector not specified");