[PATCH 5.15 090/135] net/mlx5e: Lag, Fix use-after-free in fib event handler

Greg Kroah-Hartman
2022-05-10T14:10:00Z

From: Vlad Buslov <vladbu@nvidia.com>

[ Upstream commit 27b0420fd959e38e3500e60b637d39dfab065645 ]

Recent commit that modified fib route event handler to handle events
according to their priority introduced use-after-free[0] in mp->mfi pointer
usage. The pointer now is not just cached in order to be compared to
following fib_info instances, but is also dereferenced to obtain
fib_priority. However, since mlx5 lag code doesn't hold the reference to
fin_info during whole mp->mfi lifetime, it could be used after fib_info
instance has already been freed be kernel infrastructure code.

Don't ever dereference mp->mfi pointer. Refactor it to be 'const void*'
type and cache fib_info priority in dedicated integer. Group
fib_info-related data into dedicated 'fib' structure that will be further
extended by following patches in the series.

[0]:

[ 203.588029] ==================================================================
[ 203.590161] BUG: KASAN: use-after-free in mlx5_lag_fib_update+0xabd/0xd60 [mlx5_core]
[ 203.592386] Read of size 4 at addr ffff888144df2050 by task kworker/u20:4/138

[ 203.594766] CPU: 3 PID: 138 Comm: kworker/u20:4 Tainted: G B 5.17.0-rc7+ #6
[ 203.596751] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[ 203.598813] Workqueue: mlx5_lag_mp mlx5_lag_fib_update [mlx5_core]
[ 203.600053] Call Trace:
[ 203.600608] <TASK>
[ 203.601110] dump_stack_lvl+0x48/0x5e
[ 203.601860] print_address_description.constprop.0+0x1f/0x160
[ 203.602950] ? mlx5_lag_fib_update+0xabd/0xd60 [mlx5_core]
[ 203.604073] ? mlx5_lag_fib_update+0xabd/0xd60 [mlx5_core]
[ 203.605177] kasan_report.cold+0x83/0xdf
[ 203.605969] ? mlx5_lag_fib_update+0xabd/0xd60 [mlx5_core]
[ 203.607102] mlx5_lag_fib_update+0xabd/0xd60 [mlx5_core]
[ 203.608199] ? mlx5_lag_init_fib_work+0x1c0/0x1c0 [mlx5_core]
[ 203.609382] ? read_word_at_a_time+0xe/0x20
[ 203.610463] ? strscpy+0xa0/0x2a0
[ 203.611463] process_one_work+0x722/0x1270
[ 203.612344] worker_thread+0x540/0x11e0
[ 203.613136] ? rescuer_thread+0xd50/0xd50
[ 203.613949] kthread+0x26e/0x300
[ 203.614627] ? kthread_complete_and_exit+0x20/0x20
[ 203.615542] ret_from_fork+0x1f/0x30
[ 203.616273] </TASK>

[ 203.617174] Allocated by task 3746:
[ 203.617874] kasan_save_stack+0x1e/0x40
[ 203.618644] __kasan_kmalloc+0x81/0xa0
[ 203.619394] fib_create_info+0xb41/0x3c50
[ 203.620213] fib_table_insert+0x190/0x1ff0
[ 203.621020] fib_magic.isra.0+0x246/0x2e0
[ 203.621803] fib_add_ifaddr+0x19f/0x670
[ 203.622563] fib_inetaddr_event+0x13f/0x270
[ 203.623377] blocking_notifier_call_chain+0xd4/0x130
[ 203.624355] __inet_insert_ifa+0x641/0xb20
[ 203.625185] inet_rtm_newaddr+0xc3d/0x16a0
[ 203.626009] rtnetlink_rcv_msg+0x309/0x880
[ 203.626826] netlink_rcv_skb+0x11d/0x340
[ 203.627626] netlink_unicast+0x4cc/0x790
[ 203.628430] netlink_sendmsg+0x762/0xc00
[ 203.629230] sock_sendmsg+0xb2/0xe0
[ 203.629955] ____sys_sendmsg+0x58a/0x770
[ 203.630756] ___sys_sendmsg+0xd8/0x160
[ 203.631523] __sys_sendmsg+0xb7/0x140
[ 203.632294] do_syscall_64+0x35/0x80
[ 203.633045] entry_SYSCALL_64_after_hwframe+0x44/0xae

[ 203.634427] Freed by task 0:
[ 203.635063] kasan_save_stack+0x1e/0x40
[ 203.635844] kasan_set_track+0x21/0x30
[ 203.636618] kasan_set_free_info+0x20/0x30
[ 203.637450] __kasan_slab_free+0xfc/0x140
[ 203.638271] kfree+0x94/0x3b0
[ 203.638903] rcu_core+0x5e4/0x1990
[ 203.639640] __do_softirq+0x1ba/0x5d3

[ 203.640828] Last potentially related work creation:
[ 203.641785] kasan_save_stack+0x1e/0x40
[ 203.642571] __kasan_record_aux_stack+0x9f/0xb0
[ 203.643478] call_rcu+0x88/0x9c0
[ 203.644178] fib_release_info+0x539/0x750
[ 203.644997] fib_table_delete+0x659/0xb80
[ 203.645809] fib_magic.isra.0+0x1a3/0x2e0
[ 203.646617] fib_del_ifaddr+0x93f/0x1300
[ 203.647415] fib_inetaddr_event+0x9f/0x270
[ 203.648251] blocking_notifier_call_chain+0xd4/0x130
[ 203.649225] __inet_del_ifa+0x474/0xc10
[ 203.650016] devinet_ioctl+0x781/0x17f0
[ 203.650788] inet_ioctl+0x1ad/0x290
[ 203.651533] sock_do_ioctl+0xce/0x1c0
[ 203.652315] sock_ioctl+0x27b/0x4f0
[ 203.653058] __x64_sys_ioctl+0x124/0x190
[ 203.653850] do_syscall_64+0x35/0x80
[ 203.654608] entry_SYSCALL_64_after_hwframe+0x44/0xae

[ 203.666952] The buggy address belongs to the object at ffff888144df2000
which belongs to the cache kmalloc-256 of size 256
[ 203.669250] The buggy address is located 80 bytes inside of
256-byte region [ffff888144df2000, ffff888144df2100)
[ 203.671332] The buggy address belongs to the page:
[ 203.672273] page:00000000bf6c9314 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x144df0
[ 203.674009] head:00000000bf6c9314 order:2 compound_mapcount:0 compound_pincount:0
[ 203.675422] flags: 0x2ffff800010200(slab|head|node=0|zone=2|lastcpupid=0x1ffff)
[ 203.676819] raw: 002ffff800010200 0000000000000000 dead000000000122 ffff888100042b40
[ 203.678384] raw: 0000000000000000 0000000080200020 00000001ffffffff 0000000000000000
[ 203.679928] page dumped because: kasan: bad access detected

[ 203.681455] Memory state around the buggy address:
[ 203.682421] ffff888144df1f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 203.683863] ffff888144df1f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 203.685310] >ffff888144df2000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 203.686701] ^
[ 203.687820] ffff888144df2080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 203.689226] ffff888144df2100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 203.690620] ==================================================================

Fixes: ad11c4f1d8fd ("net/mlx5e: Lag, Only handle events from highest priority multipath entry")
Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Maor Dickman <maord@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../net/ethernet/mellanox/mlx5/core/lag_mp.c | 26 ++++++++++++-------
.../net/ethernet/mellanox/mlx5/core/lag_mp.h | 5 +++-
2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lag_mp.c b/drivers/net/ethernet/mellanox/mlx5/core/lag_mp.c
index cb0a48d374a3..8d278c45e7cc 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lag_mp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lag_mp.c
@@ -100,6 +100,12 @@ static void mlx5_lag_fib_event_flush(struct notifier_block *nb)
flush_workqueue(mp->wq);
}

+static void mlx5_lag_fib_set(struct lag_mp *mp, struct fib_info *fi)
+{
+ mp->fib.mfi = fi;
+ mp->fib.priority = fi->fib_priority;
+}
+
struct mlx5_fib_event_work {
struct work_struct work;
struct mlx5_lag *ldev;
@@ -121,13 +127,13 @@ static void mlx5_lag_fib_route_event(struct mlx5_lag *ldev,
/* Handle delete event */
if (event == FIB_EVENT_ENTRY_DEL) {
/* stop track */
- if (mp->mfi == fi)
- mp->mfi = NULL;
+ if (mp->fib.mfi == fi)
+ mp->fib.mfi = NULL;
return;
}

/* Handle multipath entry with lower priority value */
- if (mp->mfi && mp->mfi != fi && fi->fib_priority >= mp->mfi->fib_priority)
+ if (mp->fib.mfi && mp->fib.mfi != fi && fi->fib_priority >= mp->fib.priority)
return;

/* Handle add/replace event */
@@ -145,7 +151,7 @@ static void mlx5_lag_fib_route_event(struct mlx5_lag *ldev,
mlx5_lag_set_port_affinity(ldev, i);
}

- mp->mfi = fi;
+ mlx5_lag_fib_set(mp, fi);
return;
}

@@ -165,7 +171,7 @@ static void mlx5_lag_fib_route_event(struct mlx5_lag *ldev,
}

/* First time we see multipath route */
- if (!mp->mfi && !__mlx5_lag_is_active(ldev)) {
+ if (!mp->fib.mfi && !__mlx5_lag_is_active(ldev)) {
struct lag_tracker tracker;

tracker = ldev->tracker;
@@ -173,7 +179,7 @@ static void mlx5_lag_fib_route_event(struct mlx5_lag *ldev,
}

mlx5_lag_set_port_affinity(ldev, MLX5_LAG_NORMAL_AFFINITY);
- mp->mfi = fi;
+ mlx5_lag_fib_set(mp, fi);
}

static void mlx5_lag_fib_nexthop_event(struct mlx5_lag *ldev,
@@ -184,7 +190,7 @@ static void mlx5_lag_fib_nexthop_event(struct mlx5_lag *ldev,
struct lag_mp *mp = &ldev->lag_mp;

/* Check the nh event is related to the route */
- if (!mp->mfi || mp->mfi != fi)
+ if (!mp->fib.mfi || mp->fib.mfi != fi)
return;

/* nh added/removed */
@@ -313,7 +319,7 @@ void mlx5_lag_mp_reset(struct mlx5_lag *ldev)
/* Clear mfi, as it might become stale when a route delete event
* has been missed, see mlx5_lag_fib_route_event().
*/
- ldev->lag_mp.mfi = NULL;
+ ldev->lag_mp.fib.mfi = NULL;
}

int mlx5_lag_mp_init(struct mlx5_lag *ldev)
@@ -324,7 +330,7 @@ int mlx5_lag_mp_init(struct mlx5_lag *ldev)
/* always clear mfi, as it might become stale when a route delete event
* has been missed
*/
- mp->mfi = NULL;
+ mp->fib.mfi = NULL;

if (mp->fib_nb.notifier_call)
return 0;
@@ -354,5 +360,5 @@ void mlx5_lag_mp_cleanup(struct mlx5_lag *ldev)
unregister_fib_notifier(&init_net, &mp->fib_nb);
destroy_workqueue(mp->wq);
mp->fib_nb.notifier_call = NULL;
- mp->mfi = NULL;
+ mp->fib.mfi = NULL;
}
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lag_mp.h b/drivers/net/ethernet/mellanox/mlx5/core/lag_mp.h
index dea199e79bed..e8380eb0dd6a 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lag_mp.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lag_mp.h
@@ -15,7 +15,10 @@ enum mlx5_lag_port_affinity {

struct lag_mp {
struct notifier_block fib_nb;
- struct fib_info *mfi; /* used in tracking fib events */
+ struct {
+ const void *mfi; /* used in tracking fib events */
+ u32 priority;
+ } fib;
struct workqueue_struct *wq;
};

--
2.35.1