[PATCH net] net: bonding: fix use-after-free after 802.3ad slave unbind

[PATCH net] net: bonding: fix use-after-free after 802.3ad slave unbind

[Yevhen Orlov]

commit 0622cab0341c ("bonding: fix 802.3ad aggregator reselection"),
resolve case, when there is several aggregation groups in the same bond.
bond_3ad_unbind_slave will invalidate (clear) aggregator when
__agg_active_ports return zero. So, ad_clear_agg can be executed even, when
num_of_ports!=0. Than bond_3ad_unbind_slave can be executed again for,
previously cleared aggregator. NOTE: at this time bond_3ad_unbind_slave
will not update slave ports list, because lag_ports==NULL. So, here we
got slave ports, pointing to freed aggregator memory.

Fix with checking actual number of ports in group (as was before
commit 0622cab0341c ("bonding: fix 802.3ad aggregator reselection") ),
before ad_clear_agg().

The KASAN logs are as follows:

[  767.617392] ==================================================================
[  767.630776] BUG: KASAN: use-after-free in bond_3ad_state_machine_handler+0x13dc/0x1470
[  767.638764] Read of size 2 at addr ffff00011ba9d430 by task kworker/u8:7/767
[  767.647361] CPU: 3 PID: 767 Comm: kworker/u8:7 Tainted: G           O 5.15.11 #15
[  767.655329] Hardware name: DNI AmazonGo1 A7040 board (DT)
[  767.660760] Workqueue: lacp_1 bond_3ad_state_machine_handler
[  767.666468] Call trace:
[  767.668930]  dump_backtrace+0x0/0x2d0
[  767.672625]  show_stack+0x24/0x30
[  767.675965]  dump_stack_lvl+0x68/0x84
[  767.679659]  print_address_description.constprop.0+0x74/0x2b8
[  767.685451]  kasan_report+0x1f0/0x260
[  767.689148]  __asan_load2+0x94/0xd0
[  767.692667]  bond_3ad_state_machine_handler+0x13dc/0x1470

Fixes: 0622cab0341c ("bonding: fix 802.3ad aggregator reselection")
Co-developed-by: Maksym Glubokiy <maksym.glubokiy@plvision.eu>
Signed-off-by: Maksym Glubokiy <maksym.glubokiy@plvision.eu>
Signed-off-by: Yevhen Orlov <yevhen.orlov@plvision.eu>
---
 drivers/net/bonding/bond_3ad.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index a86b1f71762e..d7fb33c078e8 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -2228,7 +2228,8 @@ void bond_3ad_unbind_slave(struct slave *slave)
 				temp_aggregator->num_of_ports--;
 				if (__agg_active_ports(temp_aggregator) == 0) {
 					select_new_active_agg = temp_aggregator->is_active;
-					ad_clear_agg(temp_aggregator);
+					if (temp_aggregator->num_of_ports == 0)
+						ad_clear_agg(temp_aggregator);
 					if (select_new_active_agg) {
 						slave_info(bond->dev, slave->dev, "Removing an active aggregator\n");
 						/* select new active aggregator */
-- 
2.17.1

Re: [PATCH net] net: bonding: fix use-after-free after 802.3ad slave unbind

[Jay Vosburgh]

Yevhen Orlov <yevhen.orlov@plvision.eu> wrote:

>commit 0622cab0341c ("bonding: fix 802.3ad aggregator reselection"),
>resolve case, when there is several aggregation groups in the same bond.
>bond_3ad_unbind_slave will invalidate (clear) aggregator when
>__agg_active_ports return zero. So, ad_clear_agg can be executed even, when
>num_of_ports!=0. Than bond_3ad_unbind_slave can be executed again for,
>previously cleared aggregator. NOTE: at this time bond_3ad_unbind_slave
>will not update slave ports list, because lag_ports==NULL. So, here we
>got slave ports, pointing to freed aggregator memory.
>
>Fix with checking actual number of ports in group (as was before
>commit 0622cab0341c ("bonding: fix 802.3ad aggregator reselection") ),
>before ad_clear_agg().

	To be clear, what it looks like is going on is that, after
0622cab0341c, we're getting to this point with an aggregator that
contains the port being removed and a non-zero number of inactive ports.
The extant logic is for the "old way" (no inactive ports in an agg), and
presumes that if __agg_active_ports() == 0 then the agg is empty, which
isn't a safe assumption in the current code.

Acked-by: Jay Vosburgh <jay.vosburgh@canonical.com>

	-J

>The KASAN logs are as follows:
>
>[  767.617392] ==================================================================
>[  767.630776] BUG: KASAN: use-after-free in bond_3ad_state_machine_handler+0x13dc/0x1470
>[  767.638764] Read of size 2 at addr ffff00011ba9d430 by task kworker/u8:7/767
>[  767.647361] CPU: 3 PID: 767 Comm: kworker/u8:7 Tainted: G           O 5.15.11 #15
>[  767.655329] Hardware name: DNI AmazonGo1 A7040 board (DT)
>[  767.660760] Workqueue: lacp_1 bond_3ad_state_machine_handler
>[  767.666468] Call trace:
>[  767.668930]  dump_backtrace+0x0/0x2d0
>[  767.672625]  show_stack+0x24/0x30
>[  767.675965]  dump_stack_lvl+0x68/0x84
>[  767.679659]  print_address_description.constprop.0+0x74/0x2b8
>[  767.685451]  kasan_report+0x1f0/0x260
>[  767.689148]  __asan_load2+0x94/0xd0
>[  767.692667]  bond_3ad_state_machine_handler+0x13dc/0x1470
>
>Fixes: 0622cab0341c ("bonding: fix 802.3ad aggregator reselection")
>Co-developed-by: Maksym Glubokiy <maksym.glubokiy@plvision.eu>
>Signed-off-by: Maksym Glubokiy <maksym.glubokiy@plvision.eu>
>Signed-off-by: Yevhen Orlov <yevhen.orlov@plvision.eu>
>---
> drivers/net/bonding/bond_3ad.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
>index a86b1f71762e..d7fb33c078e8 100644
>--- a/drivers/net/bonding/bond_3ad.c
>+++ b/drivers/net/bonding/bond_3ad.c
>@@ -2228,7 +2228,8 @@ void bond_3ad_unbind_slave(struct slave *slave)
> 				temp_aggregator->num_of_ports--;
> 				if (__agg_active_ports(temp_aggregator) == 0) {
> 					select_new_active_agg = temp_aggregator->is_active;
>-					ad_clear_agg(temp_aggregator);
>+					if (temp_aggregator->num_of_ports == 0)
>+						ad_clear_agg(temp_aggregator);
> 					if (select_new_active_agg) {
> 						slave_info(bond->dev, slave->dev, "Removing an active aggregator\n");
> 						/* select new active aggregator */
>-- 
>2.17.1
>

Re: [PATCH net] net: bonding: fix use-after-free after 802.3ad slave unbind

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 29 Jun 2022 04:29:14 +0300 you wrote:
> commit 0622cab0341c ("bonding: fix 802.3ad aggregator reselection"),
> resolve case, when there is several aggregation groups in the same bond.
> bond_3ad_unbind_slave will invalidate (clear) aggregator when
> __agg_active_ports return zero. So, ad_clear_agg can be executed even, when
> num_of_ports!=0. Than bond_3ad_unbind_slave can be executed again for,
> previously cleared aggregator. NOTE: at this time bond_3ad_unbind_slave
> will not update slave ports list, because lag_ports==NULL. So, here we
> got slave ports, pointing to freed aggregator memory.
> 
> [...]

Here is the summary with links:
  - [net] net: bonding: fix use-after-free after 802.3ad slave unbind
    https://git.kernel.org/netdev/net/c/050133e1aa2c

You are awesome, thank you!
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