Re: [PATCH net] rtnetlink: invoke 'cb->done' destructor before 'cb->args' reset
On 11/1/18 7:42 AM, Alexey Kodanev wrote:
> On 11/01/2018 04:11 PM, Alexey Kodanev wrote:
>> On 10/31/2018 08:35 PM, David Ahern wrote:
>>> On 10/31/18 10:55 AM, David Ahern wrote:
I think the simplest fix for 4.20 is to break the loop if ret is non-0 -
restore the previous behavior.
>>>
>>> that is the only recourse. It has to bail if ret is non-0. Do you want
>>> to send a patch with that fix?
>>>
>>
>> I see, and inet6_dump_fib() cleanups fib6_walker if ret is zero. Will send
>> the fix.
>
> Can it happen that inet6_dump_fib() returns skb->len (0) in the below cases?
>
> * if (arg.filter.flags & RTM_F_CLONED)
> return skb->len;
>
> ...
>
> w = (void *)cb->args[2];
> if (!w) {
> ...
> w = kzalloc(...)
> ...
>
> * if (arg.filter.table_id) {
> ...
> if (!tb) {
> if (arg.filter.dump_all_families)
> return skb->len;
>
>
> Would it be safer to add "res = skb->len; goto out;" instead of "return
> skb->len;"
> so that it can call fib6_dump_end() for "res <= 0"? Or use cb->data instead of
> cb->args?
>
Since res is initialized to 0, both of those can just be 'goto out;'
The break in dump_all is still needed though.
Re: [PATCH net] rtnetlink: invoke 'cb->done' destructor before 'cb->args' reset
On 11/01/2018 04:11 PM, Alexey Kodanev wrote:
> On 10/31/2018 08:35 PM, David Ahern wrote:
>> On 10/31/18 10:55 AM, David Ahern wrote:
>>> I think the simplest fix for 4.20 is to break the loop if ret is non-0 -
>>> restore the previous behavior.
>>
>> that is the only recourse. It has to bail if ret is non-0. Do you want
>> to send a patch with that fix?
>>
>
> I see, and inet6_dump_fib() cleanups fib6_walker if ret is zero. Will send
> the fix.
Can it happen that inet6_dump_fib() returns skb->len (0) in the below cases?
* if (arg.filter.flags & RTM_F_CLONED)
return skb->len;
...
w = (void *)cb->args[2];
if (!w) {
...
w = kzalloc(...)
...
* if (arg.filter.table_id) {
...
if (!tb) {
if (arg.filter.dump_all_families)
return skb->len;
Would it be safer to add "res = skb->len; goto out;" instead of "return
skb->len;"
so that it can call fib6_dump_end() for "res <= 0"? Or use cb->data instead of
cb->args?
Re: [PATCH net] rtnetlink: invoke 'cb->done' destructor before 'cb->args' reset
On 10/31/2018 08:35 PM, David Ahern wrote: > On 10/31/18 10:55 AM, David Ahern wrote: >> I think the simplest fix for 4.20 is to break the loop if ret is non-0 - >> restore the previous behavior. > > that is the only recourse. It has to bail if ret is non-0. Do you want > to send a patch with that fix? > I see, and inet6_dump_fib() cleanups fib6_walker if ret is zero. Will send the fix.
Re: [PATCH net] rtnetlink: invoke 'cb->done' destructor before 'cb->args' reset
On 10/31/18 10:55 AM, David Ahern wrote: > I think the simplest fix for 4.20 is to break the loop if ret is non-0 - > restore the previous behavior. that is the only recourse. It has to bail if ret is non-0. Do you want to send a patch with that fix?
Re: [PATCH net] rtnetlink: invoke 'cb->done' destructor before 'cb->args' reset
On 10/31/18 12:42 AM, Alexey Kodanev wrote:
> cb->args[2] can store the pointer to the struct fib6_walker,
> allocated in inet6_dump_fib(). On the next loop iteration in
> rtnl_dump_all(), 'memset(, 0, sizeof(cb->args))' can reset
> that pointer, leaking the memory [1].
>
> Fix it by calling cb->done, if it is set, before filling 'cb->args'
> with zeros.
>
> Looks like the recent changes in rtnl_dump_all() contributed to
> the appearance of this kmemleak [1], commit c63586dc9b3e ("net:
> rtnl_dump_all needs to propagate error from dumpit function")
> breaks the loop only on an error now.
>
...
It is more efficient to keep going.
I think the simplest fix for 4.20 is to break the loop if ret is non-0 -
restore the previous behavior. For net-next I think the done callback is
not needed for ipv6; I think there is a simpler way to do it.
Re: [PATCH net] rtnetlink: invoke 'cb->done' destructor before 'cb->args' reset
On 31.10.2018 09:42, Alexey Kodanev wrote:
> cb->args[2] can store the pointer to the struct fib6_walker,
> allocated in inet6_dump_fib(). On the next loop iteration in
> rtnl_dump_all(), 'memset(, 0, sizeof(cb->args))' can reset
> that pointer, leaking the memory [1].
>
On the second thought we could as well save the state of fib6_walker
in inet6_dump_fib() with cb->data. That should fix the leak too.
Is it sounds reasonable?
Thanks,
Alexey
> Fix it by calling cb->done, if it is set, before filling 'cb->args'
> with zeros.
>
> Looks like the recent changes in rtnl_dump_all() contributed to
> the appearance of this kmemleak [1], commit c63586dc9b3e ("net:
> rtnl_dump_all needs to propagate error from dumpit function")
> breaks the loop only on an error now.
>
> [1]:
> unreferenced object 0x88001322a200 (size 96):
> comm "sshd", pid 1484, jiffies 4296032768 (age 1432.542s)
> hex dump (first 32 bytes):
> 00 01 00 00 00 00 ad de 00 02 00 00 00 00 ad de
> 18 09 41 36 00 88 ff ff 18 09 41 36 00 88 ff ff ..A6..A6
> backtrace:
> [<95846b39>] kmem_cache_alloc_trace+0x151/0x220
> [<7d12709f>] inet6_dump_fib+0x68d/0x940
> [<2775a316>] rtnl_dump_all+0x1d9/0x2d0
> [] netlink_dump+0x945/0x11a0
> [<2f43485f>] __netlink_dump_start+0x55d/0x800
> [] rtnetlink_rcv_msg+0x4fa/0xa00
> [<9b5761f3>] netlink_rcv_skb+0x29c/0x420
> [<87a1dae1>] rtnetlink_rcv+0x15/0x20
> [<691b703b>] netlink_unicast+0x4e3/0x6c0
> [] netlink_sendmsg+0x7f2/0xba0
> [<96d2aa60>] sock_sendmsg+0xba/0xf0
> [<8c1b786f>] __sys_sendto+0x1e4/0x330
> [<19587b3f>] __x64_sys_sendto+0xe1/0x1a0
> [<071f4d56>] do_syscall_64+0x9f/0x300
> [<2737577f>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [<57587684>] 0x
>
> Fixes: 1b43af5480c3 ("[IPV6]: Increase number of possible routing tables to
> 2^32")
> Signed-off-by: Alexey Kodanev
> ---
> net/core/rtnetlink.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index f679c7a..314c683 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -3362,6 +3362,8 @@ static int rtnl_dump_all(struct sk_buff *skb, struct
> netlink_callback *cb)
> continue;
>
> if (idx > s_idx) {
> + if (cb->done)
> + cb->done(cb);
> memset(>args[0], 0, sizeof(cb->args));
> cb->prev_seq = 0;
> cb->seq = 0;
>
[PATCH net] rtnetlink: invoke 'cb->done' destructor before 'cb->args' reset
cb->args[2] can store the pointer to the struct fib6_walker,
allocated in inet6_dump_fib(). On the next loop iteration in
rtnl_dump_all(), 'memset(, 0, sizeof(cb->args))' can reset
that pointer, leaking the memory [1].
Fix it by calling cb->done, if it is set, before filling 'cb->args'
with zeros.
Looks like the recent changes in rtnl_dump_all() contributed to
the appearance of this kmemleak [1], commit c63586dc9b3e ("net:
rtnl_dump_all needs to propagate error from dumpit function")
breaks the loop only on an error now.
[1]:
unreferenced object 0x88001322a200 (size 96):
comm "sshd", pid 1484, jiffies 4296032768 (age 1432.542s)
hex dump (first 32 bytes):
00 01 00 00 00 00 ad de 00 02 00 00 00 00 ad de
18 09 41 36 00 88 ff ff 18 09 41 36 00 88 ff ff ..A6..A6
backtrace:
[<95846b39>] kmem_cache_alloc_trace+0x151/0x220
[<7d12709f>] inet6_dump_fib+0x68d/0x940
[<2775a316>] rtnl_dump_all+0x1d9/0x2d0
[] netlink_dump+0x945/0x11a0
[<2f43485f>] __netlink_dump_start+0x55d/0x800
[] rtnetlink_rcv_msg+0x4fa/0xa00
[<9b5761f3>] netlink_rcv_skb+0x29c/0x420
[<87a1dae1>] rtnetlink_rcv+0x15/0x20
[<691b703b>] netlink_unicast+0x4e3/0x6c0
[] netlink_sendmsg+0x7f2/0xba0
[<96d2aa60>] sock_sendmsg+0xba/0xf0
[<8c1b786f>] __sys_sendto+0x1e4/0x330
[<19587b3f>] __x64_sys_sendto+0xe1/0x1a0
[<071f4d56>] do_syscall_64+0x9f/0x300
[<2737577f>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[<57587684>] 0x
Fixes: 1b43af5480c3 ("[IPV6]: Increase number of possible routing tables to
2^32")
Signed-off-by: Alexey Kodanev
---
net/core/rtnetlink.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index f679c7a..314c683 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3362,6 +3362,8 @@ static int rtnl_dump_all(struct sk_buff *skb, struct
netlink_callback *cb)
continue;
if (idx > s_idx) {
+ if (cb->done)
+ cb->done(cb);
memset(>args[0], 0, sizeof(cb->args));
cb->prev_seq = 0;
cb->seq = 0;
--
1.8.3.1
