On Mon, Mar 14, 2022 at 12:53:20PM +0100, Greg Kroah-Hartman wrote:
From: Anirudh Rayabharam mail@anirudhrb.com
[ Upstream commit e2ae38cf3d91837a493cb2093c87700ff3cbe667 ]
This breaks batching of IOTLB messages. [1] fixes it but hasn't landed in Linus' tree yet.
[1]: https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git/commit/?h=linu...
- Anirudh.
In vhost_iotlb_add_range_ctx(), range size can overflow to 0 when start is 0 and last is ULONG_MAX. One instance where it can happen is when userspace sends an IOTLB message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an entry with size = 0, start = 0, last = ULONG_MAX ends up in the iotlb. Next time a packet is sent, iotlb_access_ok() loops indefinitely due to that erroneous entry.
Call Trace: <TASK> iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340 vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366 vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104 vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372 kthread+0x2e9/0x3a0 kernel/kthread.c:377 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK>
Reported by syzbot at: https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
To fix this, do two things:
- Return -EINVAL in vhost_chr_write_iter() when userspace asks to map a range with size 0.
- Fix vhost_iotlb_add_range_ctx() to handle the range [0, ULONG_MAX] by splitting it into two entries.
Fixes: 0bbe30668d89e ("vhost: factor out IOTLB") Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com Signed-off-by: Anirudh Rayabharam mail@anirudhrb.com Link: https://lore.kernel.org/r/20220305095525.5145-1-mail@anirudhrb.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org
drivers/vhost/iotlb.c | 11 +++++++++++ drivers/vhost/vhost.c | 5 +++++ 2 files changed, 16 insertions(+)
diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c index 670d56c879e5..40b098320b2a 100644 --- a/drivers/vhost/iotlb.c +++ b/drivers/vhost/iotlb.c @@ -57,6 +57,17 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb, if (last < start) return -EFAULT;
- /* If the range being mapped is [0, ULONG_MAX], split it into two entries
* otherwise its size would overflow u64.*/- if (start == 0 && last == ULONG_MAX) {
u64 mid = last / 2;vhost_iotlb_add_range_ctx(iotlb, start, mid, addr, perm, opaque);addr += mid + 1;start = mid + 1;- }
- if (iotlb->limit && iotlb->nmaps == iotlb->limit && iotlb->flags & VHOST_IOTLB_FLAG_RETIRE) {
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 59edb5a1ffe2..55475fd59fb7 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1170,6 +1170,11 @@ ssize_t vhost_chr_write_iter(struct vhost_dev *dev, goto done; }
- if (msg.size == 0) {
ret = -EINVAL;goto done;- }
- if (dev->msg_handler) ret = dev->msg_handler(dev, &msg); else
-- 2.34.1