KASAN: use-after-free Read in free_netdev

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syzbot

unread,
Mar 7, 2020, 5:14:15 AM3/7/20
to syzkaller...@googlegroups.com
Hello,

syzbot found the following crash on:

HEAD commit: 7472c402 Linux 4.19.108
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17bab01de00000
kernel config: https://syzkaller.appspot.com/x/.config?x=6d889e71eea7bde
dashboard link: https://syzkaller.appspot.com/bug?extid=aeb990c485fd48663c5a
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+aeb990...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in free_netdev+0x3b0/0x420 net/core/dev.c:9219
Read of size 8 at addr ffff88804d814c60 by task syz-executor.5/11936

CPU: 1 PID: 11936 Comm: syz-executor.5 Not tainted 4.19.108-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x188/0x20d lib/dump_stack.c:118
print_address_description.cold+0x7c/0x212 mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report mm/kasan/report.c:412 [inline]
kasan_report.cold+0x88/0x2b9 mm/kasan/report.c:396
free_netdev+0x3b0/0x420 net/core/dev.c:9219
netdev_run_todo+0x5ea/0x740 net/core/dev.c:8972
rtnl_unlock net/core/rtnetlink.c:117 [inline]
rtnetlink_rcv_msg+0x460/0xaf0 net/core/rtnetlink.c:4778
netlink_rcv_skb+0x160/0x410 net/netlink/af_netlink.c:2455
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x4d7/0x6a0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x80b/0xcd0 net/netlink/af_netlink.c:1909
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:632
___sys_sendmsg+0x803/0x920 net/socket.c:2115
__sys_sendmsg+0xec/0x1b0 net/socket.c:2153
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c4a9
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f0fbdcf5c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f0fbdcf66d4 RCX: 000000000045c4a9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000005
RBP: 000000000076c060 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000009f9 R14: 00000000004cc766 R15: 000000000076c06c

Allocated by task 11930:
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc mm/kasan/kasan.c:553 [inline]
kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:531
__do_kmalloc mm/slab.c:3727 [inline]
__kmalloc+0x15b/0x770 mm/slab.c:3736
kmalloc include/linux/slab.h:520 [inline]
sk_prot_alloc+0x18c/0x2d0 net/core/sock.c:1466
sk_alloc+0x36/0xf50 net/core/sock.c:1520
tun_chr_open+0x7b/0x560 drivers/net/tun.c:3224
misc_open+0x372/0x4a0 drivers/char/misc.c:141
chrdev_open+0x219/0x5c0 fs/char_dev.c:423
do_dentry_open+0x4a8/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x1031/0x4200 fs/namei.c:3537
do_filp_open+0x1a1/0x280 fs/namei.c:3567
do_sys_open+0x3c0/0x500 fs/open.c:1088
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 11929:
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0xf7/0x140 mm/kasan/kasan.c:521
__cache_free mm/slab.c:3503 [inline]
kfree+0xce/0x220 mm/slab.c:3822
sk_prot_free net/core/sock.c:1503 [inline]
__sk_destruct+0x579/0x780 net/core/sock.c:1583
sk_destruct+0xb9/0xf0 net/core/sock.c:1598
__sk_free+0xc2/0x2e0 net/core/sock.c:1609
sk_free+0x3b/0x50 net/core/sock.c:1620
sock_put include/net/sock.h:1707 [inline]
__tun_detach+0xa04/0x1020 drivers/net/tun.c:742
tun_detach drivers/net/tun.c:754 [inline]
tun_chr_close+0x10e/0x180 drivers/net/tun.c:3261
__fput+0x2cd/0x890 fs/file_table.c:278
task_work_run+0x13f/0x1b0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:193 [inline]
exit_to_usermode_loop+0x25a/0x2b0 arch/x86/entry/common.c:167
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88804d8145c0
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 1696 bytes inside of
4096-byte region [ffff88804d8145c0, ffff88804d8155c0)
The buggy address belongs to the page:
page:ffffea0001360500 count:1 mapcount:0 mapping:ffff88812c3dcdc0 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea000139d108 ffffea0002107a08 ffff88812c3dcdc0
raw: 0000000000000000 ffff88804d8145c0 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88804d814b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88804d814b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88804d814c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88804d814c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88804d814d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
ubi0: attached mtd0 (name "mtdram test device", size 0 MiB)


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

syzbot

unread,
Mar 7, 2020, 6:31:12 AM3/7/20
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following crash on:

HEAD commit: 7472c402 Linux 4.19.108
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1696aa2de00000
kernel config: https://syzkaller.appspot.com/x/.config?x=6d889e71eea7bde
dashboard link: https://syzkaller.appspot.com/bug?extid=aeb990c485fd48663c5a
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1606b01de00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+aeb990...@syzkaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
audit: type=1400 audit(1583580449.448:41): avc: denied { associate } for pid=7978 comm="syz-executor.0" name="syz0" scontext=unconfined_u:object_r:unlabeled_t:s0 tcontext=system_u:object_r:unlabeled_t:s0 tclass=filesystem permissive=1
==================================================================
BUG: KASAN: use-after-free in free_netdev+0x3b0/0x420 net/core/dev.c:9219
Read of size 8 at addr ffff8880a3944d60 by task syz-executor.0/8027

CPU: 0 PID: 8027 Comm: syz-executor.0 Not tainted 4.19.108-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x188/0x20d lib/dump_stack.c:118
print_address_description.cold+0x7c/0x212 mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report mm/kasan/report.c:412 [inline]
kasan_report.cold+0x88/0x2b9 mm/kasan/report.c:396
free_netdev+0x3b0/0x420 net/core/dev.c:9219
netdev_run_todo+0x5ea/0x740 net/core/dev.c:8972
rtnl_unlock net/core/rtnetlink.c:117 [inline]
rtnetlink_rcv_msg+0x460/0xaf0 net/core/rtnetlink.c:4778
netlink_rcv_skb+0x160/0x410 net/netlink/af_netlink.c:2455
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x4d7/0x6a0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x80b/0xcd0 net/netlink/af_netlink.c:1909
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:632
___sys_sendmsg+0x803/0x920 net/socket.c:2115
__sys_sendmsg+0xec/0x1b0 net/socket.c:2153
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c4a9
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fa636214c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fa6362156d4 RCX: 000000000045c4a9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000005
RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000009f9 R14: 00000000004cc766 R15: 000000000076bfcc

Allocated by task 8026:
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc mm/kasan/kasan.c:553 [inline]
kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:531
__do_kmalloc mm/slab.c:3727 [inline]
__kmalloc+0x15b/0x770 mm/slab.c:3736
kmalloc include/linux/slab.h:520 [inline]
sk_prot_alloc+0x18c/0x2d0 net/core/sock.c:1466
sk_alloc+0x36/0xf50 net/core/sock.c:1520
tun_chr_open+0x7b/0x560 drivers/net/tun.c:3224
misc_open+0x372/0x4a0 drivers/char/misc.c:141
chrdev_open+0x219/0x5c0 fs/char_dev.c:423
do_dentry_open+0x4a8/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x1031/0x4200 fs/namei.c:3537
do_filp_open+0x1a1/0x280 fs/namei.c:3567
do_sys_open+0x3c0/0x500 fs/open.c:1088
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8024:
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0xf7/0x140 mm/kasan/kasan.c:521
__cache_free mm/slab.c:3503 [inline]
kfree+0xce/0x220 mm/slab.c:3822
sk_prot_free net/core/sock.c:1503 [inline]
__sk_destruct+0x579/0x780 net/core/sock.c:1583
sk_destruct+0xb9/0xf0 net/core/sock.c:1598
__sk_free+0xc2/0x2e0 net/core/sock.c:1609
sk_free+0x3b/0x50 net/core/sock.c:1620
sock_put include/net/sock.h:1707 [inline]
__tun_detach+0xa04/0x1020 drivers/net/tun.c:742
tun_detach drivers/net/tun.c:754 [inline]
tun_chr_close+0x10e/0x180 drivers/net/tun.c:3261
__fput+0x2cd/0x890 fs/file_table.c:278
task_work_run+0x13f/0x1b0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:193 [inline]
exit_to_usermode_loop+0x25a/0x2b0 arch/x86/entry/common.c:167
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880a39446c0
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 1696 bytes inside of
4096-byte region [ffff8880a39446c0, ffff8880a39456c0)
The buggy address belongs to the page:
page:ffffea00028e5100 count:1 mapcount:0 mapping:ffff88812c3dcdc0 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea000284ed88 ffffea000295b008 ffff88812c3dcdc0
raw: 0000000000000000 ffff8880a39446c0 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a3944c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a3944c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a3944d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a3944d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a3944e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

syzbot

unread,
Mar 8, 2020, 6:52:11 AM3/8/20
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following crash on:

HEAD commit: 7472c402 Linux 4.19.108
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=119689fde00000
kernel config: https://syzkaller.appspot.com/x/.config?x=6d889e71eea7bde
dashboard link: https://syzkaller.appspot.com/bug?extid=aeb990c485fd48663c5a
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17bb37b5e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1379e1fde00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+aeb990...@syzkaller.appspotmail.com

device veth0_macvtap left promiscuous mode
device veth0_macvtap left promiscuous mode
==================================================================
BUG: KASAN: use-after-free in free_netdev+0x3b0/0x420 net/core/dev.c:9219
Read of size 8 at addr ffff88809029a9e0 by task syz-executor011/8729

CPU: 1 PID: 8729 Comm: syz-executor011 Not tainted 4.19.108-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x188/0x20d lib/dump_stack.c:118
print_address_description.cold+0x7c/0x212 mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report mm/kasan/report.c:412 [inline]
kasan_report.cold+0x88/0x2b9 mm/kasan/report.c:396
free_netdev+0x3b0/0x420 net/core/dev.c:9219
netdev_run_todo+0x5ea/0x740 net/core/dev.c:8972
rtnl_unlock net/core/rtnetlink.c:117 [inline]
rtnetlink_rcv_msg+0x460/0xaf0 net/core/rtnetlink.c:4778
netlink_rcv_skb+0x160/0x410 net/netlink/af_netlink.c:2455
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x4d7/0x6a0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x80b/0xcd0 net/netlink/af_netlink.c:1909
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:632
___sys_sendmsg+0x803/0x920 net/socket.c:2115
__sys_sendmsg+0xec/0x1b0 net/socket.c:2153
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x449c29
Code: e8 3c e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 ab 06 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fa2aae6fd98 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006dfc98 RCX: 0000000000449c29
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000005
RBP: 00000000006dfc90 R08: 00007fa2aae70700 R09: 0000000000000000
R10: 00007fa2aae70700 R11: 0000000000000246 R12: 00000000006dfc9c
R13: 0000003065736f72 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 8724:
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc mm/kasan/kasan.c:553 [inline]
kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:531
__do_kmalloc mm/slab.c:3727 [inline]
__kmalloc+0x15b/0x770 mm/slab.c:3736
kmalloc include/linux/slab.h:520 [inline]
sk_prot_alloc+0x18c/0x2d0 net/core/sock.c:1466
sk_alloc+0x36/0xf50 net/core/sock.c:1520
tun_chr_open+0x7b/0x560 drivers/net/tun.c:3224
misc_open+0x372/0x4a0 drivers/char/misc.c:141
chrdev_open+0x219/0x5c0 fs/char_dev.c:423
do_dentry_open+0x4a8/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x1031/0x4200 fs/namei.c:3537
do_filp_open+0x1a1/0x280 fs/namei.c:3567
do_sys_open+0x3c0/0x500 fs/open.c:1088
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8725:
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0xf7/0x140 mm/kasan/kasan.c:521
__cache_free mm/slab.c:3503 [inline]
kfree+0xce/0x220 mm/slab.c:3822
sk_prot_free net/core/sock.c:1503 [inline]
__sk_destruct+0x579/0x780 net/core/sock.c:1583
sk_destruct+0xb9/0xf0 net/core/sock.c:1598
__sk_free+0xc2/0x2e0 net/core/sock.c:1609
sk_free+0x3b/0x50 net/core/sock.c:1620
sock_put include/net/sock.h:1707 [inline]
__tun_detach+0xa04/0x1020 drivers/net/tun.c:742
tun_detach drivers/net/tun.c:754 [inline]
tun_chr_close+0x10e/0x180 drivers/net/tun.c:3261
__fput+0x2cd/0x890 fs/file_table.c:278
task_work_run+0x13f/0x1b0 kernel/task_work.c:113
get_signal+0x1b83/0x1f90 kernel/signal.c:2394
do_signal+0x8f/0x1710 arch/x86/kernel/signal.c:821
exit_to_usermode_loop+0x22b/0x2b0 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88809029a340
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 1696 bytes inside of
4096-byte region [ffff88809029a340, ffff88809029b340)
The buggy address belongs to the page:
page:ffffea000240a680 count:1 mapcount:0 mapping:ffff88812c3dcdc0 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea0001f1b688 ffffea0001f17c88 ffff88812c3dcdc0
raw: 0000000000000000 ffff88809029a340 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809029a880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809029a900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88809029a980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88809029aa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809029aa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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