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![]() The ax25_kill_by_device() will set s->ax25_dev = NULL and call ax25_disconnect() to change states of ax25_cb and sock, if we call ax25_bind() before ax25_kill_by_device(). However, if we call ax25_bind() again between the window of ax25_kill_by_device() and ax25_dev_device_down(), the values and states changed by ax25_kill_by_device() will be reassigned. Finally, ax25_dev_device_down() will deallocate net_device. If we dereference net_device in syscall functions such as ax25_release(), ax25_sendmsg(), ax25_getsockopt(), ax25_getname() and ax25_info_show(), a UAF bug will occur. One of the possible race conditions is shown below: (USE) | (FREE) ax25_bind() | | ax25_kill_by_device() ax25_bind() | ax25_connect() | ... | ax25_dev_device_down() | ... | dev_put_track(dev, ...) //FREE ax25_release() | ... ax25_send_control() | alloc_skb() //USE | the corresponding fail log is shown below: =============================================================== BUG: KASAN: use-after-free in ax25_send_control+0x43/0x210 ... Call Trace: ... ax25_send_control+0x43/0x210 ax25_release+0x2db/0x3b0 __sock_release+0x6d/0x120 sock_close+0xf/0x20 __fput+0x11f/0x420 ... Allocated by task 1283: ... __kasan_kmalloc+0x81/0xa0 alloc_netdev_mqs+0x5a/0x680 mkiss_open+0x6c/0x380 tty_ldisc_open+0x55/0x90 ... Freed by task 1969: ... kfree+0xa3/0x2c0 device_release+0x54/0xe0 kobject_put+0xa5/0x120 tty_ldisc_kill+0x3e/0x80 ... In order to fix these UAF bugs caused by rebinding operation, this patch adds dev_hold_track() into ax25_bind() and corresponding dev_put_track() into ax25_kill_by_device(). Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> Signed-off-by: David S. Miller <davem@davemloft.net> |
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.. | ||
af_ax25.c | ||
ax25_addr.c | ||
ax25_dev.c | ||
ax25_ds_in.c | ||
ax25_ds_subr.c | ||
ax25_ds_timer.c | ||
ax25_iface.c | ||
ax25_in.c | ||
ax25_ip.c | ||
ax25_out.c | ||
ax25_route.c | ||
ax25_std_in.c | ||
ax25_std_subr.c | ||
ax25_std_timer.c | ||
ax25_subr.c | ||
ax25_timer.c | ||
ax25_uid.c | ||
Kconfig | ||
Makefile | ||
sysctl_net_ax25.c |