From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit bf64ff4c2aac65d680dc639a511c781cf6b6ec08 ]
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 jiri@mellanox.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/genetlink.h | 2 -- net/netlink/genetlink.c | 48 +++++++++++++----------------------------------- 2 files changed, 13 insertions(+), 37 deletions(-)
--- a/include/net/genetlink.h +++ b/include/net/genetlink.h @@ -35,7 +35,6 @@ struct genl_info; * do additional, common, filtering and return an error * @post_doit: called after an operation's doit callback, it may * undo operations done by pre_doit, for example release locks - * @attrbuf: buffer to store parsed attributes (private) * @mcgrps: multicast groups used by this family * @n_mcgrps: number of multicast groups * @mcgrp_offset: starting number of multicast group IDs in this family @@ -58,7 +57,6 @@ struct genl_family { void (*post_doit)(const struct genl_ops *ops, struct sk_buff *skb, struct genl_info *info); - struct nlattr ** attrbuf; /* private */ const struct genl_ops * ops; const struct genl_multicast_group *mcgrps; unsigned int n_ops; --- a/net/netlink/genetlink.c +++ b/net/netlink/genetlink.c @@ -351,22 +351,11 @@ int genl_register_family(struct genl_fam start = end = GENL_ID_VFS_DQUOT; }
- if (family->maxattr && !family->parallel_ops) { - family->attrbuf = kmalloc_array(family->maxattr + 1, - sizeof(struct nlattr *), - GFP_KERNEL); - if (family->attrbuf == NULL) { - err = -ENOMEM; - goto errout_locked; - } - } else - family->attrbuf = NULL; - family->id = idr_alloc_cyclic(&genl_fam_idr, family, start, end + 1, GFP_KERNEL); if (family->id < 0) { err = family->id; - goto errout_free; + goto errout_locked; }
err = genl_validate_assign_mc_groups(family); @@ -385,8 +374,6 @@ int genl_register_family(struct genl_fam
errout_remove: idr_remove(&genl_fam_idr, family->id); -errout_free: - kfree(family->attrbuf); errout_locked: genl_unlock_all(); return err; @@ -419,8 +406,6 @@ int genl_unregister_family(const struct atomic_read(&genl_sk_destructing_cnt) == 0); genl_unlock();
- kfree(family->attrbuf); - genl_ctrl_event(CTRL_CMD_DELFAMILY, family, NULL, 0);
return 0; @@ -485,30 +470,23 @@ genl_family_rcv_msg_attrs_parse(const st if (!family->maxattr) return NULL;
- if (family->parallel_ops) { - attrbuf = kmalloc_array(family->maxattr + 1, - sizeof(struct nlattr *), GFP_KERNEL); - if (!attrbuf) - return ERR_PTR(-ENOMEM); - } else { - attrbuf = family->attrbuf; - } + attrbuf = kmalloc_array(family->maxattr + 1, + sizeof(struct nlattr *), GFP_KERNEL); + if (!attrbuf) + return ERR_PTR(-ENOMEM);
err = __nlmsg_parse(nlh, hdrlen, attrbuf, family->maxattr, family->policy, validate, extack); if (err) { - if (family->parallel_ops) - kfree(attrbuf); + kfree(attrbuf); return ERR_PTR(err); } return attrbuf; }
-static void genl_family_rcv_msg_attrs_free(const struct genl_family *family, - struct nlattr **attrbuf) +static void genl_family_rcv_msg_attrs_free(struct nlattr **attrbuf) { - if (family->parallel_ops) - kfree(attrbuf); + kfree(attrbuf); }
struct genl_start_context { @@ -542,7 +520,7 @@ static int genl_start(struct netlink_cal no_attrs: info = genl_dumpit_info_alloc(); if (!info) { - genl_family_rcv_msg_attrs_free(ctx->family, attrs); + genl_family_rcv_msg_attrs_free(attrs); return -ENOMEM; } info->family = ctx->family; @@ -559,7 +537,7 @@ no_attrs: }
if (rc) { - genl_family_rcv_msg_attrs_free(info->family, info->attrs); + genl_family_rcv_msg_attrs_free(info->attrs); genl_dumpit_info_free(info); cb->data = NULL; } @@ -588,7 +566,7 @@ static int genl_lock_done(struct netlink rc = ops->done(cb); genl_unlock(); } - genl_family_rcv_msg_attrs_free(info->family, info->attrs); + genl_family_rcv_msg_attrs_free(info->attrs); genl_dumpit_info_free(info); return rc; } @@ -601,7 +579,7 @@ static int genl_parallel_done(struct net
if (ops->done) rc = ops->done(cb); - genl_family_rcv_msg_attrs_free(info->family, info->attrs); + genl_family_rcv_msg_attrs_free(info->attrs); genl_dumpit_info_free(info); return rc; } @@ -694,7 +672,7 @@ static int genl_family_rcv_msg_doit(cons family->post_doit(ops, skb, &info);
out: - genl_family_rcv_msg_attrs_free(family, attrbuf); + genl_family_rcv_msg_attrs_free(attrbuf);
return err; }