Hello,
syzbot has tested the proposed patch but the reproducer still triggered crash:
KASAN: use-after-free Read in htc_connect_service
usb 4-1: Service connection timeout for: 256
==================================================================
BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
BUG: KASAN: use-after-free in refcount_read include/linux/refcount.h:134 [inline]
BUG: KASAN: use-after-free in skb_unref include/linux/skbuff.h:1042 [inline]
BUG: KASAN: use-after-free in kfree_skb+0x32/0x3d0 net/core/skbuff.c:692
Read of size 4 at addr ffff8881c7ec2d54 by task kworker/0:5/3237
CPU: 0 PID: 3237 Comm: kworker/0:5 Not tainted 5.6.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events request_firmware_work_func
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0xef/0x16e lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd3/0x314 mm/kasan/report.c:374
__kasan_report.cold+0x37/0x77 mm/kasan/report.c:506
kasan_report+0xe/0x20 mm/kasan/common.c:641
check_memory_region_inline mm/kasan/generic.c:185 [inline]
check_memory_region+0x152/0x1c0 mm/kasan/generic.c:192
atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
refcount_read include/linux/refcount.h:134 [inline]
skb_unref include/linux/skbuff.h:1042 [inline]
kfree_skb+0x32/0x3d0 net/core/skbuff.c:692
htc_connect_service.cold+0xa9/0x109 drivers/net/wireless/ath/ath9k/htc_hst.c:282
ath9k_wmi_connect+0xd2/0x1a0 drivers/net/wireless/ath/ath9k/wmi.c:265
ath9k_init_htc_services.constprop.0+0xb4/0x650 drivers/net/wireless/ath/ath9k/htc_drv_init.c:146
ath9k_htc_probe_device+0x25a/0x1d80 drivers/net/wireless/ath/ath9k/htc_drv_init.c:959
ath9k_htc_hw_init+0x31/0x60 drivers/net/wireless/ath/ath9k/htc_hst.c:501
ath9k_hif_usb_firmware_cb+0x26b/0x500 drivers/net/wireless/ath/ath9k/hif_usb.c:1192
request_firmware_work_func+0x126/0x242 drivers/base/firmware_loader/main.c:976
process_one_work+0x94b/0x1620 kernel/workqueue.c:2266
worker_thread+0x96/0xe20 kernel/workqueue.c:2412
kthread+0x318/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Allocated by task 3237:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:515 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:488
slab_post_alloc_hook mm/slab.h:584 [inline]
slab_alloc_node mm/slub.c:2786 [inline]
kmem_cache_alloc_node+0xdc/0x330 mm/slub.c:2822
__alloc_skb+0xba/0x5a0 net/core/skbuff.c:198
alloc_skb include/linux/skbuff.h:1081 [inline]
htc_connect_service+0x2cc/0x840 drivers/net/wireless/ath/ath9k/htc_hst.c:257
ath9k_wmi_connect+0xd2/0x1a0 drivers/net/wireless/ath/ath9k/wmi.c:265
ath9k_init_htc_services.constprop.0+0xb4/0x650 drivers/net/wireless/ath/ath9k/htc_drv_init.c:146
ath9k_htc_probe_device+0x25a/0x1d80 drivers/net/wireless/ath/ath9k/htc_drv_init.c:959
ath9k_htc_hw_init+0x31/0x60 drivers/net/wireless/ath/ath9k/htc_hst.c:501
ath9k_hif_usb_firmware_cb+0x26b/0x500 drivers/net/wireless/ath/ath9k/hif_usb.c:1192
request_firmware_work_func+0x126/0x242 drivers/base/firmware_loader/main.c:976
process_one_work+0x94b/0x1620 kernel/workqueue.c:2266
worker_thread+0x96/0xe20 kernel/workqueue.c:2412
kthread+0x318/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Freed by task 0:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:337 [inline]
__kasan_slab_free+0x117/0x160 mm/kasan/common.c:476
slab_free_hook mm/slub.c:1444 [inline]
slab_free_freelist_hook mm/slub.c:1477 [inline]
slab_free mm/slub.c:3034 [inline]
kmem_cache_free+0x9b/0x360 mm/slub.c:3050
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]
kfree_skb net/core/skbuff.c:696 [inline]
kfree_skb+0x102/0x3d0 net/core/skbuff.c:690
ath9k_htc_txcompletion_cb+0x1f8/0x2b0 drivers/net/wireless/ath/ath9k/htc_hst.c:356
hif_usb_regout_cb+0x10b/0x1b0 drivers/net/wireless/ath/ath9k/hif_usb.c:90
__usb_hcd_giveback_urb+0x1f2/0x470 drivers/usb/core/hcd.c:1648
usb_hcd_giveback_urb+0x368/0x420 drivers/usb/core/hcd.c:1713
dummy_timer+0x1258/0x32ae drivers/usb/gadget/udc/dummy_hcd.c:1966
call_timer_fn+0x195/0x6f0 kernel/time/timer.c:1404
expire_timers kernel/time/timer.c:1449 [inline]
__run_timers kernel/time/timer.c:1773 [inline]
__run_timers kernel/time/timer.c:1740 [inline]
run_timer_softirq+0x5f9/0x1500 kernel/time/timer.c:1786
__do_softirq+0x21e/0x950 kernel/softirq.c:292
The buggy address belongs to the object at ffff8881c7ec2c80
which belongs to the cache skbuff_head_cache of size 224
The buggy address is located 212 bytes inside of
224-byte region [ffff8881c7ec2c80, ffff8881c7ec2d60)
The buggy address belongs to the page:
page:ffffea00071fb080 refcount:1 mapcount:0 mapping:ffff8881da16b400 index:0x0
flags: 0x200000000000200(slab)
raw: 0200000000000200 dead000000000100 dead000000000122 ffff8881da16b400
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8881c7ec2c00: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881c7ec2c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881c7ec2d00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
^
ffff8881c7ec2d80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff8881c7ec2e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Tested on:
commit: 0fa84af8 Merge tag 'usb-serial-5.7-rc1' of https://git.ker..
git tree: https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=17c2dadbe00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a782c087b1f425c6
dashboard link: https://syzkaller.appspot.com/bug?extid=d403396d4df67ad0bd5f
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
patch: https://syzkaller.appspot.com/x/patch.diff?x=14b7b40be00000
