From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit c36f05559104b66bcd7f617e931e38c680227b74 ]
There are two kinds of memory leaks in genl_family_rcv_msg_dumpit():
1. Before we call ops->start(), whenever an error happens, we forget to free the memory allocated in genl_family_rcv_msg_dumpit().
2. When ops->start() fails, the 'info' has been already installed on the per socket control block, so we should not free it here. More importantly, nlk->cb_running is still false at this point, so netlink_sock_destruct() cannot free it either.
The first kind of memory leaks is easier to resolve, but the second one requires some deeper thoughts.
After reviewing how netfilter handles this, the most elegant solution I find is just to use a similar way to allocate the memory, that is, moving memory allocations from caller into ops->start(). With this, we can solve both kinds of memory leaks: for 1), no memory allocation happens before ops->start(); for 2), ops->start() handles its own failures and 'info' is installed to the socket control block only when success. The only ugliness here is we have to pass all local variables on stack via a struct, but this is not hard to understand.
Alternatively, we can introduce a ops->free() to solve this too, but it is overkill as only genetlink has this problem so far.
Fixes: 1927f41a22a0 ("net: genetlink: introduce dump info struct to be available during dumpit op") Reported-by: syzbot+21f04f481f449c8db840@syzkaller.appspotmail.com Cc: "Jason A. Donenfeld" Jason@zx2c4.com Cc: Florian Westphal fw@strlen.de Cc: Pablo Neira Ayuso pablo@netfilter.org Cc: Jiri Pirko jiri@mellanox.com Cc: YueHaibing yuehaibing@huawei.com Cc: Shaochun Chen cscnull@gmail.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 --- net/netlink/genetlink.c | 94 +++++++++++++++++++++++++++++------------------- 1 file changed, 58 insertions(+), 36 deletions(-)
--- a/net/netlink/genetlink.c +++ b/net/netlink/genetlink.c @@ -513,15 +513,58 @@ static void genl_family_rcv_msg_attrs_fr kfree(attrbuf); }
-static int genl_lock_start(struct netlink_callback *cb) +struct genl_start_context { + const struct genl_family *family; + struct nlmsghdr *nlh; + struct netlink_ext_ack *extack; + const struct genl_ops *ops; + int hdrlen; +}; + +static int genl_start(struct netlink_callback *cb) { - const struct genl_ops *ops = genl_dumpit_info(cb)->ops; + struct genl_start_context *ctx = cb->data; + const struct genl_ops *ops = ctx->ops; + struct genl_dumpit_info *info; + struct nlattr **attrs = NULL; int rc = 0;
+ if (ops->validate & GENL_DONT_VALIDATE_DUMP) + goto no_attrs; + + if (ctx->nlh->nlmsg_len < nlmsg_msg_size(ctx->hdrlen)) + return -EINVAL; + + attrs = genl_family_rcv_msg_attrs_parse(ctx->family, ctx->nlh, ctx->extack, + ops, ctx->hdrlen, + GENL_DONT_VALIDATE_DUMP_STRICT, + true); + if (IS_ERR(attrs)) + return PTR_ERR(attrs); + +no_attrs: + info = genl_dumpit_info_alloc(); + if (!info) { + kfree(attrs); + return -ENOMEM; + } + info->family = ctx->family; + info->ops = ops; + info->attrs = attrs; + + cb->data = info; if (ops->start) { - genl_lock(); + if (!ctx->family->parallel_ops) + genl_lock(); rc = ops->start(cb); - genl_unlock(); + if (!ctx->family->parallel_ops) + genl_unlock(); + } + + if (rc) { + kfree(attrs); + genl_dumpit_info_free(info); + cb->data = NULL; } return rc; } @@ -548,7 +591,7 @@ static int genl_lock_done(struct netlink rc = ops->done(cb); genl_unlock(); } - genl_family_rcv_msg_attrs_free(info->family, info->attrs, true); + genl_family_rcv_msg_attrs_free(info->family, info->attrs, false); genl_dumpit_info_free(info); return rc; } @@ -573,43 +616,23 @@ static int genl_family_rcv_msg_dumpit(co const struct genl_ops *ops, int hdrlen, struct net *net) { - struct genl_dumpit_info *info; - struct nlattr **attrs = NULL; + struct genl_start_context ctx; int err;
if (!ops->dumpit) return -EOPNOTSUPP;
- if (ops->validate & GENL_DONT_VALIDATE_DUMP) - goto no_attrs; - - if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen)) - return -EINVAL; - - attrs = genl_family_rcv_msg_attrs_parse(family, nlh, extack, - ops, hdrlen, - GENL_DONT_VALIDATE_DUMP_STRICT, - true); - if (IS_ERR(attrs)) - return PTR_ERR(attrs); - -no_attrs: - /* Allocate dumpit info. It is going to be freed by done() callback. */ - info = genl_dumpit_info_alloc(); - if (!info) { - genl_family_rcv_msg_attrs_free(family, attrs, true); - return -ENOMEM; - } - - info->family = family; - info->ops = ops; - info->attrs = attrs; + ctx.family = family; + ctx.nlh = nlh; + ctx.extack = extack; + ctx.ops = ops; + ctx.hdrlen = hdrlen;
if (!family->parallel_ops) { struct netlink_dump_control c = { .module = family->module, - .data = info, - .start = genl_lock_start, + .data = &ctx, + .start = genl_start, .dump = genl_lock_dumpit, .done = genl_lock_done, }; @@ -617,12 +640,11 @@ no_attrs: genl_unlock(); err = __netlink_dump_start(net->genl_sock, skb, nlh, &c); genl_lock(); - } else { struct netlink_dump_control c = { .module = family->module, - .data = info, - .start = ops->start, + .data = &ctx, + .start = genl_start, .dump = ops->dumpit, .done = genl_parallel_done, };