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Subject[PATCH] net/smc: check for missing nlattrs in SMC_PNETID messages
Date
From: Eric Biggers <ebiggers@google.com>

It's possible to crash the kernel in several different ways by sending
messages to the SMC_PNETID generic netlink family that are missing the
expected attributes:

- Missing SMC_PNETID_NAME => null pointer dereference when comparing
names.
- Missing SMC_PNETID_ETHNAME => null pointer dereference accessing
smc_pnetentry::ndev.
- Missing SMC_PNETID_IBNAME => null pointer dereference accessing
smc_pnetentry::smcibdev.
- Missing SMC_PNETID_IBPORT => out of bounds array access to
smc_ib_device::pattr[-1].

Fix it by validating that all expected attributes are present and that
SMC_PNETID_IBPORT is nonzero.

Reported-by: syzbot+5cd61039dc9b8bfa6e47@syzkaller.appspotmail.com
Fixes: 6812baabf24d ("smc: establish pnet table management")
Cc: <stable@vger.kernel.org> # v4.11+
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
net/smc/smc_pnet.c | 71 ++++++++++++++++++++++++++--------------------
1 file changed, 40 insertions(+), 31 deletions(-)

diff --git a/net/smc/smc_pnet.c b/net/smc/smc_pnet.c
index 74568cdbca708..d7b88b2d1b224 100644
--- a/net/smc/smc_pnet.c
+++ b/net/smc/smc_pnet.c
@@ -245,40 +245,45 @@ static struct smc_ib_device *smc_pnet_find_ib(char *ib_name)
static int smc_pnet_fill_entry(struct net *net, struct smc_pnetentry *pnetelem,
struct nlattr *tb[])
{
- char *string, *ibname = NULL;
- int rc = 0;
+ char *string, *ibname;
+ int rc;

memset(pnetelem, 0, sizeof(*pnetelem));
INIT_LIST_HEAD(&pnetelem->list);
- if (tb[SMC_PNETID_NAME]) {
- string = (char *)nla_data(tb[SMC_PNETID_NAME]);
- if (!smc_pnetid_valid(string, pnetelem->pnet_name)) {
- rc = -EINVAL;
- goto error;
- }
- }
- if (tb[SMC_PNETID_ETHNAME]) {
- string = (char *)nla_data(tb[SMC_PNETID_ETHNAME]);
- pnetelem->ndev = dev_get_by_name(net, string);
- if (!pnetelem->ndev)
- return -ENOENT;
- }
- if (tb[SMC_PNETID_IBNAME]) {
- ibname = (char *)nla_data(tb[SMC_PNETID_IBNAME]);
- ibname = strim(ibname);
- pnetelem->smcibdev = smc_pnet_find_ib(ibname);
- if (!pnetelem->smcibdev) {
- rc = -ENOENT;
- goto error;
- }
- }
- if (tb[SMC_PNETID_IBPORT]) {
- pnetelem->ib_port = nla_get_u8(tb[SMC_PNETID_IBPORT]);
- if (pnetelem->ib_port > SMC_MAX_PORTS) {
- rc = -EINVAL;
- goto error;
- }
- }
+
+ rc = -EINVAL;
+ if (!tb[SMC_PNETID_NAME])
+ goto error;
+ string = (char *)nla_data(tb[SMC_PNETID_NAME]);
+ if (!smc_pnetid_valid(string, pnetelem->pnet_name))
+ goto error;
+
+ rc = -EINVAL;
+ if (!tb[SMC_PNETID_ETHNAME])
+ goto error;
+ rc = -ENOENT;
+ string = (char *)nla_data(tb[SMC_PNETID_ETHNAME]);
+ pnetelem->ndev = dev_get_by_name(net, string);
+ if (!pnetelem->ndev)
+ goto error;
+
+ rc = -EINVAL;
+ if (!tb[SMC_PNETID_IBNAME])
+ goto error;
+ rc = -ENOENT;
+ ibname = (char *)nla_data(tb[SMC_PNETID_IBNAME]);
+ ibname = strim(ibname);
+ pnetelem->smcibdev = smc_pnet_find_ib(ibname);
+ if (!pnetelem->smcibdev)
+ goto error;
+
+ rc = -EINVAL;
+ if (!tb[SMC_PNETID_IBPORT])
+ goto error;
+ pnetelem->ib_port = nla_get_u8(tb[SMC_PNETID_IBPORT]);
+ if (pnetelem->ib_port < 1 || pnetelem->ib_port > SMC_MAX_PORTS)
+ goto error;
+
return 0;

error:
@@ -307,6 +312,8 @@ static int smc_pnet_get(struct sk_buff *skb, struct genl_info *info)
void *hdr;
int rc;

+ if (!info->attrs[SMC_PNETID_NAME])
+ return -EINVAL;
pnetelem = smc_pnet_find_pnetid(
(char *)nla_data(info->attrs[SMC_PNETID_NAME]));
if (!pnetelem)
@@ -359,6 +366,8 @@ static int smc_pnet_add(struct sk_buff *skb, struct genl_info *info)

static int smc_pnet_del(struct sk_buff *skb, struct genl_info *info)
{
+ if (!info->attrs[SMC_PNETID_NAME])
+ return -EINVAL;
return smc_pnet_remove_by_pnetid(
(char *)nla_data(info->attrs[SMC_PNETID_NAME]));
}
--
2.17.0
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