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SubjectRe: [PATCH -next] bonding: Fix a use-after-free problem when bond_sysfs_slave_add() failed
From
On 02.11.21 03:55, huangguobin wrote:
> I think bond_sysfs_slave_del should not be used in the error handling process, because bond_sysfs_slave_del will traverse all slave_attrs and release them. When sysfs_create_file fails, only some attributes may be created successfully.

[please don't top-post]

The suggestion was to use sysfs_create_files(), which would handle such rollback
internally. There was no mention of using bond_sysfs_slave_del().

ie. something like the following (untested):

diff --git a/drivers/net/bonding/bond_sysfs_slave.c b/drivers/net/bonding/bond_sysfs_slave.c
index fd07561da034..a1fd4bc0b0d2 100644
--- a/drivers/net/bonding/bond_sysfs_slave.c
+++ b/drivers/net/bonding/bond_sysfs_slave.c
@@ -108,15 +108,15 @@ static ssize_t ad_partner_oper_port_state_show(struct slave *slave, char *buf)
}
static SLAVE_ATTR_RO(ad_partner_oper_port_state);

-static const struct slave_attribute *slave_attrs[] = {
- &slave_attr_state,
- &slave_attr_mii_status,
- &slave_attr_link_failure_count,
- &slave_attr_perm_hwaddr,
- &slave_attr_queue_id,
- &slave_attr_ad_aggregator_id,
- &slave_attr_ad_actor_oper_port_state,
- &slave_attr_ad_partner_oper_port_state,
+static const struct attribute *slave_attrs[] = {
+ &slave_attr_state.attr,
+ &slave_attr_mii_status.attr,
+ &slave_attr_link_failure_count.attr,
+ &slave_attr_perm_hwaddr.attr,
+ &slave_attr_queue_id.attr,
+ &slave_attr_ad_aggregator_id.attr,
+ &slave_attr_ad_actor_oper_port_state.attr,
+ &slave_attr_ad_partner_oper_port_state.attr,
NULL
};

@@ -137,24 +137,16 @@ const struct sysfs_ops slave_sysfs_ops = {

int bond_sysfs_slave_add(struct slave *slave)
{
- const struct slave_attribute **a;
int err;

- for (a = slave_attrs; *a; ++a) {
- err = sysfs_create_file(&slave->kobj, &((*a)->attr));
- if (err) {
- kobject_put(&slave->kobj);
- return err;
- }
- }
+ err = sysfs_create_files(&slave->kobj, slave_attrs);
+ if (err)
+ kobject_put(&slave->kobj);

- return 0;
+ return err;
}

void bond_sysfs_slave_del(struct slave *slave)
{
- const struct slave_attribute **a;
-
- for (a = slave_attrs; *a; ++a)
- sysfs_remove_file(&slave->kobj, &((*a)->attr));
+ sysfs_remove_files(&slave->kobj, slave_attrs);
}

> -----Original Message-----
> From: Julian Wiedmann [mailto:jwi@linux.ibm.com]
> Sent: Tuesday, November 2, 2021 3:31 AM
> To: huangguobin <huangguobin4@huawei.com>; j.vosburgh@gmail.com; vfalico@gmail.com; andy@greyhouse.net; davem@davemloft.net; kuba@kernel.org
> Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH -next] bonding: Fix a use-after-free problem when bond_sysfs_slave_add() failed
>
> On 01.11.21 15:34, Huang Guobin wrote:
>> When I do fuzz test for bonding device interface, I got the following
>> use-after-free Calltrace:
>>
>
> [...]
>
>> Fixes: 7afcaec49696 (bonding: use kobject_put instead of _del after
>> kobject_add)
>> Signed-off-by: Huang Guobin <huangguobin4@huawei.com>
>> ---
>> drivers/net/bonding/bond_sysfs_slave.c | 11 ++++++++---
>> 1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/bonding/bond_sysfs_slave.c
>> b/drivers/net/bonding/bond_sysfs_slave.c
>> index fd07561..d1a5b3f 100644
>> --- a/drivers/net/bonding/bond_sysfs_slave.c
>> +++ b/drivers/net/bonding/bond_sysfs_slave.c
>> @@ -137,18 +137,23 @@ static ssize_t slave_show(struct kobject *kobj,
>>
>> int bond_sysfs_slave_add(struct slave *slave) {
>> - const struct slave_attribute **a;
>> + const struct slave_attribute **a, **b;
>> int err;
>>
>> for (a = slave_attrs; *a; ++a) {
>> err = sysfs_create_file(&slave->kobj, &((*a)->attr));
>> if (err) {
>> - kobject_put(&slave->kobj);
>> - return err;
>> + goto err_remove_file;
>> }
>> }
>>
>> return 0;
>> +
>> +err_remove_file:
>> + for (b = slave_attrs; b < a; ++b)
>> + sysfs_remove_file(&slave->kobj, &((*b)->attr));
>> +
>> + return err;
>> }
>>
>
> This looks like a candidate for sysfs_create_files(), no?
>
>> void bond_sysfs_slave_del(struct slave *slave)
>>
>

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