From: Xu Jia xujia39@huawei.com
[ Upstream commit 2b04495e21cdb9b45c28c6aeb2da560184de20a3 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/hamradio/6pack.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c index 45c3c4a1101b..9fb567524220 100644 --- a/drivers/net/hamradio/6pack.c +++ b/drivers/net/hamradio/6pack.c @@ -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); + } } }