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hamradio: 6pack: fix array-index-out-of-bounds in decode_std_command()

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Hulk Robot reports incorrect sp->rx_count_cooked value in decode_std_command().
This should be caused by the subtracting from sp->rx_count_cooked before.
It seems that sp->rx_count_cooked value is changed to 0, which bypassed the
previous judgment.

The situation is shown below:

         (Thread 1)			|  (Thread 2)
decode_std_command()		| resync_tnc()
...					|
if (rest == 2)			|
	sp->rx_count_cooked -= 2;	|
else if (rest == 3)			| ...
					| sp->rx_count_cooked = 0;
	sp->rx_count_cooked -= 1;	|
for (i = 0; i < sp->rx_count_cooked; i++) // report error
	checksum += sp->cooked_buf[i];

sp->rx_count_cooked is a shared variable but is not protected by a lock.
The same applies to sp->rx_count. This patch adds a lock to fix the bug.

The fail log is shown below:
=======================================================================
UBSAN: array-index-out-of-bounds in drivers/net/hamradio/6pack.c:925:31
index 400 is out of range for type 'unsigned char [400]'
CPU: 3 PID: 7433 Comm: kworker/u10:1 Not tainted 5.18.0-rc5-00163-g4b97bac0756a #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 dump_stack_lvl+0xcd/0x134
 ubsan_epilogue+0xb/0x50
 __ubsan_handle_out_of_bounds.cold+0x62/0x6c
 sixpack_receive_buf+0xfda/0x1330
 tty_ldisc_receive_buf+0x13e/0x180
 tty_port_default_receive_buf+0x6d/0xa0
 flush_to_ldisc+0x213/0x3f0
 process_one_work+0x98f/0x1620
 worker_thread+0x665/0x1080
 kthread+0x2e9/0x3a0
 ret_from_fork+0x1f/0x30
 ...

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Xu Jia <xujia39@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xu Jia 2022-06-17 17:31:06 +08:00 committed by David S. Miller
parent 911600bf5a
commit 2b04495e21
1 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/net/hamradio/6pack.c
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@ -99,6 +99,7 @@ struct sixpack {
unsigned int rx_count;
unsigned int rx_count_cooked;
spinlock_t rxlock;
int mtu; /* Our mtu (to spot changes!) */
int buffsize; /* Max buffers sizes */
@ -565,6 +566,7 @@ static int sixpack_open(struct tty_struct *tty)
sp->dev = dev;
spin_lock_init(&sp->lock);
spin_lock_init(&sp->rxlock);
refcount_set(&sp->refcnt, 1);
init_completion(&sp->dead);
@ -913,6 +915,7 @@ static void decode_std_command(struct sixpack *sp, unsigned char cmd)
sp->led_state = 0x60;
/* fill trailing bytes with zeroes */
sp->tty->ops->write(sp->tty, &sp->led_state, 1);
spin_lock_bh(&sp->rxlock);
rest = sp->rx_count;
if (rest != 0)
for (i = rest; i <= 3; i++)
@ -930,6 +933,7 @@ static void decode_std_command(struct sixpack *sp, unsigned char cmd)
sp_bump(sp, 0);
}
sp->rx_count_cooked = 0;
spin_unlock_bh(&sp->rxlock);
}
break;
case SIXP_TX_URUN: printk(KERN_DEBUG "6pack: TX underrun\n");
@ -959,8 +963,11 @@ sixpack_decode(struct sixpack *sp, const unsigned char *pre_rbuff, int count)
decode_prio_command(sp, inbyte);
else if ((inbyte & SIXP_STD_CMD_MASK) != 0)
decode_std_command(sp, inbyte);
else if ((sp->status & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK)
else if ((sp->status & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK) {
spin_lock_bh(&sp->rxlock);
decode_data(sp, inbyte);
spin_unlock_bh(&sp->rxlock);
}
}
}