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3c34fb0bd4
When releasing a socket in ax25_release(), we call netdev_put() to
decrease the refcount on the associated ax.25 device. However, the
execution path for accepting an incoming connection never calls
netdev_hold(). This imbalance leads to refcount errors, and ultimately
to kernel crashes.
A typical call trace for the above situation will start with one of the
following errors:
refcount_t: decrement hit 0; leaking memory.
refcount_t: underflow; use-after-free.
And will then have a trace like:
Call Trace:
<TASK>
? show_regs+0x64/0x70
? __warn+0x83/0x120
? refcount_warn_saturate+0xb2/0x100
? report_bug+0x158/0x190
? prb_read_valid+0x20/0x30
? handle_bug+0x3e/0x70
? exc_invalid_op+0x1c/0x70
? asm_exc_invalid_op+0x1f/0x30
? refcount_warn_saturate+0xb2/0x100
? refcount_warn_saturate+0xb2/0x100
ax25_release+0x2ad/0x360
__sock_release+0x35/0xa0
sock_close+0x19/0x20
[...]
On reboot (or any attempt to remove the interface), the kernel gets
stuck in an infinite loop:
unregister_netdevice: waiting for ax0 to become free. Usage count = 0
This patch corrects these issues by ensuring that we call netdev_hold()
and ax25_dev_hold() for new connections in ax25_accept(). This makes the
logic leading to ax25_accept() match the logic for ax25_bind(): in both
cases we increment the refcount, which is ultimately decremented in
ax25_release().
Fixes:
|
||
|---|---|---|
| .. | ||
| 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 | ||