Syzbot found the use of uninitialzied memory when injecting non conformant
CANFD frames via a tun device into the kernel:
| BUG: KMSAN: uninit-value in number+0x9f8/0x2000 lib/vsprintf.c:459
| CPU: 1 PID: 11897 Comm: syz-executor136 Not tainted 5.6.0-rc2-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+0x1c9/0x220 lib/dump_stack.c:118
| kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
| __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
| number+0x9f8/0x2000 lib/vsprintf.c:459
| vsnprintf+0x1d85/0x31b0 lib/vsprintf.c:2640
| vscnprintf+0xc2/0x180 lib/vsprintf.c:2677
| vprintk_store+0xef/0x11d0 kernel/printk/printk.c:1917
| vprintk_emit+0x2c0/0x860 kernel/printk/printk.c:1984
| vprintk_default+0x90/0xa0 kernel/printk/printk.c:2029
| vprintk_func+0x636/0x820 kernel/printk/printk_safe.c:386
| printk+0x18b/0x1d3 kernel/printk/printk.c:2062
| canfd_rcv+0x370/0x3a0 net/can/af_can.c:697
| __netif_receive_skb_one_core net/core/dev.c:5198 [inline]
| __netif_receive_skb net/core/dev.c:5312 [inline]
| netif_receive_skb_internal net/core/dev.c:5402 [inline]
| netif_receive_skb+0xe77/0xf20 net/core/dev.c:5461
| tun_rx_batched include/linux/skbuff.h:4321 [inline]
| tun_get_user+0x6aef/0x6f60 drivers/net/tun.c:1997
| tun_chr_write_iter+0x1f2/0x360 drivers/net/tun.c:2026
| call_write_iter include/linux/fs.h:1901 [inline]
| new_sync_write fs/read_write.c:483 [inline]
| __vfs_write+0xa5a/0xca0 fs/read_write.c:496
| vfs_write+0x44a/0x8f0 fs/read_write.c:558
| ksys_write+0x267/0x450 fs/read_write.c:611
| __do_sys_write fs/read_write.c:623 [inline]
| __se_sys_write+0x92/0xb0 fs/read_write.c:620
| __x64_sys_write+0x4a/0x70 fs/read_write.c:620
| do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
| entry_SYSCALL_64_after_hwframe+0x44/0xa9
In canfd_rcv() the non conformant CANFD frame (i.e. skb too short) is detected,
but the pr_warn_once() accesses uninitialized memory or the skb->data out of
bounds to print the warning message.
This problem exists in both can_rcv() and canfd_rcv(). This patch removes the
access to the skb->data from the pr_warn_once() in both functions.
Reported-by: syzbot+9bcb0c9409066696d3aa@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
---
net/can/af_can.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 7511bfae2e0d..bd37922b0c9e 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -677,8 +677,8 @@ static int can_rcv(struct sk_buff *skb, struct net_device *dev,
if (unlikely(dev->type != ARPHRD_CAN || skb->len != CAN_MTU ||
cfd->len > CAN_MAX_DLEN)) {
- pr_warn_once("PF_CAN: dropped non conform CAN skbuf: dev type %d, len %d, datalen %d\n",
- dev->type, skb->len, cfd->len);
+ pr_warn_once("PF_CAN: dropped non conform CAN skbuf: dev type %d, len %d\n",
+ dev->type, skb->len);
kfree_skb(skb);
return NET_RX_DROP;
}
@@ -694,8 +694,8 @@ static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
if (unlikely(dev->type != ARPHRD_CAN || skb->len != CANFD_MTU ||
cfd->len > CANFD_MAX_DLEN)) {
- pr_warn_once("PF_CAN: dropped non conform CAN FD skbuf: dev type %d, len %d, datalen %d\n",
- dev->type, skb->len, cfd->len);
+ pr_warn_once("PF_CAN: dropped non conform CAN FD skbuf: dev type %d, len %d\n",
+ dev->type, skb->len);
kfree_skb(skb);
return NET_RX_DROP;
}
--
2.25.0
