From: Amit Cohen amcohen@nvidia.com
[ Upstream commit 0daf2bf5a2dcf33d446b76360908f109816e2e21 ]
Each EMAD transaction stores the skb used to issue the EMAD request ('trans->tx_skb') so that the request could be retried in case of a timeout. The skb can be freed when a corresponding response is received or as part of the retry logic (e.g., failed retransmit, exceeded maximum number of retries).
The two tasks (i.e., response processing and retransmits) are synchronized by the atomic 'trans->active' field which ensures that responses to inactive transactions are ignored.
In case of a failed retransmit the transaction is finished and all of its resources are freed. However, the current code does not mark it as inactive. Syzkaller was able to hit a race condition in which a concurrent response is processed while the transaction's resources are being freed, resulting in a use-after-free [1].
Fix the issue by making sure to mark the transaction as inactive after a failed retransmit and free its resources only if a concurrent task did not already do that.
[1] BUG: KASAN: use-after-free in consume_skb+0x30/0x370 net/core/skbuff.c:833 Read of size 4 at addr ffff88804f570494 by task syz-executor.0/1004
CPU: 0 PID: 1004 Comm: syz-executor.0 Not tainted 5.8.0-rc7+ #68 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xf6/0x16e lib/dump_stack.c:118 print_address_description.constprop.0+0x1c/0x250 mm/kasan/report.c:383 __kasan_report mm/kasan/report.c:513 [inline] kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 check_memory_region_inline mm/kasan/generic.c:186 [inline] check_memory_region+0x14e/0x1b0 mm/kasan/generic.c:192 instrument_atomic_read include/linux/instrumented.h:56 [inline] atomic_read include/asm-generic/atomic-instrumented.h:27 [inline] refcount_read include/linux/refcount.h:147 [inline] skb_unref include/linux/skbuff.h:1044 [inline] consume_skb+0x30/0x370 net/core/skbuff.c:833 mlxsw_emad_trans_finish+0x64/0x1c0 drivers/net/ethernet/mellanox/mlxsw/core.c:592 mlxsw_emad_process_response drivers/net/ethernet/mellanox/mlxsw/core.c:651 [inline] mlxsw_emad_rx_listener_func+0x5c9/0xac0 drivers/net/ethernet/mellanox/mlxsw/core.c:672 mlxsw_core_skb_receive+0x4df/0x770 drivers/net/ethernet/mellanox/mlxsw/core.c:2063 mlxsw_pci_cqe_rdq_handle drivers/net/ethernet/mellanox/mlxsw/pci.c:595 [inline] mlxsw_pci_cq_tasklet+0x12a6/0x2520 drivers/net/ethernet/mellanox/mlxsw/pci.c:651 tasklet_action_common.isra.0+0x13f/0x3e0 kernel/softirq.c:550 __do_softirq+0x223/0x964 kernel/softirq.c:292 asm_call_on_stack+0x12/0x20 arch/x86/entry/entry_64.S:711
Allocated by task 1006: save_stack+0x1b/0x40 mm/kasan/common.c:48 set_track mm/kasan/common.c:56 [inline] __kasan_kmalloc mm/kasan/common.c:494 [inline] __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:467 slab_post_alloc_hook mm/slab.h:586 [inline] slab_alloc_node mm/slub.c:2824 [inline] slab_alloc mm/slub.c:2832 [inline] kmem_cache_alloc+0xcd/0x2e0 mm/slub.c:2837 __build_skb+0x21/0x60 net/core/skbuff.c:311 __netdev_alloc_skb+0x1e2/0x360 net/core/skbuff.c:464 netdev_alloc_skb include/linux/skbuff.h:2810 [inline] mlxsw_emad_alloc drivers/net/ethernet/mellanox/mlxsw/core.c:756 [inline] mlxsw_emad_reg_access drivers/net/ethernet/mellanox/mlxsw/core.c:787 [inline] mlxsw_core_reg_access_emad+0x1ab/0x1420 drivers/net/ethernet/mellanox/mlxsw/core.c:1817 mlxsw_reg_trans_query+0x39/0x50 drivers/net/ethernet/mellanox/mlxsw/core.c:1831 mlxsw_sp_sb_pm_occ_clear drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c:260 [inline] mlxsw_sp_sb_occ_max_clear+0xbff/0x10a0 drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c:1365 mlxsw_devlink_sb_occ_max_clear+0x76/0xb0 drivers/net/ethernet/mellanox/mlxsw/core.c:1037 devlink_nl_cmd_sb_occ_max_clear_doit+0x1ec/0x280 net/core/devlink.c:1765 genl_family_rcv_msg_doit net/netlink/genetlink.c:669 [inline] genl_family_rcv_msg net/netlink/genetlink.c:714 [inline] genl_rcv_msg+0x617/0x980 net/netlink/genetlink.c:731 netlink_rcv_skb+0x152/0x440 net/netlink/af_netlink.c:2470 genl_rcv+0x24/0x40 net/netlink/genetlink.c:742 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline] netlink_unicast+0x53a/0x750 net/netlink/af_netlink.c:1330 netlink_sendmsg+0x850/0xd90 net/netlink/af_netlink.c:1919 sock_sendmsg_nosec net/socket.c:651 [inline] sock_sendmsg+0x150/0x190 net/socket.c:671 ____sys_sendmsg+0x6d8/0x840 net/socket.c:2359 ___sys_sendmsg+0xff/0x170 net/socket.c:2413 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2446 do_syscall_64+0x56/0xa0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 73: save_stack+0x1b/0x40 mm/kasan/common.c:48 set_track mm/kasan/common.c:56 [inline] kasan_set_free_info mm/kasan/common.c:316 [inline] __kasan_slab_free+0x12c/0x170 mm/kasan/common.c:455 slab_free_hook mm/slub.c:1474 [inline] slab_free_freelist_hook mm/slub.c:1507 [inline] slab_free mm/slub.c:3072 [inline] kmem_cache_free+0xbe/0x380 mm/slub.c:3088 kfree_skbmem net/core/skbuff.c:622 [inline] kfree_skbmem+0xef/0x1b0 net/core/skbuff.c:616 __kfree_skb net/core/skbuff.c:679 [inline] consume_skb net/core/skbuff.c:837 [inline] consume_skb+0xe1/0x370 net/core/skbuff.c:831 mlxsw_emad_trans_finish+0x64/0x1c0 drivers/net/ethernet/mellanox/mlxsw/core.c:592 mlxsw_emad_transmit_retry.isra.0+0x9d/0xc0 drivers/net/ethernet/mellanox/mlxsw/core.c:613 mlxsw_emad_trans_timeout_work+0x43/0x50 drivers/net/ethernet/mellanox/mlxsw/core.c:625 process_one_work+0xa3e/0x17a0 kernel/workqueue.c:2269 worker_thread+0x9e/0x1050 kernel/workqueue.c:2415 kthread+0x355/0x470 kernel/kthread.c:291 ret_from_fork+0x22/0x30 arch/x86/entry/entry_64.S:293
The buggy address belongs to the object at ffff88804f5703c0 which belongs to the cache skbuff_head_cache of size 224 The buggy address is located 212 bytes inside of 224-byte region [ffff88804f5703c0, ffff88804f5704a0) The buggy address belongs to the page: page:ffffea00013d5c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0x100000000000200(slab) raw: 0100000000000200 dead000000000100 dead000000000122 ffff88806c625400 raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff88804f570380: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ffff88804f570400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88804f570480: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
^ ffff88804f570500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88804f570580: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
Fixes: caf7297e7ab5f ("mlxsw: core: Introduce support for asynchronous EMAD register access") Signed-off-by: Amit Cohen amcohen@nvidia.com Reviewed-by: Jiri Pirko jiri@nvidia.com Signed-off-by: Ido Schimmel idosch@nvidia.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/mellanox/mlxsw/core.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/net/ethernet/mellanox/mlxsw/core.c b/drivers/net/ethernet/mellanox/mlxsw/core.c index 808d924dbe21e..bdf29d0cf4d77 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/core.c +++ b/drivers/net/ethernet/mellanox/mlxsw/core.c @@ -485,6 +485,9 @@ static void mlxsw_emad_transmit_retry(struct mlxsw_core *mlxsw_core, err = mlxsw_emad_transmit(trans->core, trans); if (err == 0) return; + + if (!atomic_dec_and_test(&trans->active)) + return; } else { err = -EIO; }