Messages in this thread | | | Date | Sat, 23 Nov 2019 09:18:15 -0800 | Subject | Re: Re: Re: possible deadlock in mon_bin_vma_fault | From | syzbot <> |
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> On Fri, 22 Nov 2019, syzbot wrote:
>> > #syz test: linux-4.19.y f6e27dbb1afa
>> "linux-4.19.y" does not look like a valid git repo address.
> Let's try again. The "git tree" value in the original bug report was > "upstream", so I'll use that even though it doesn't look like a valid > git repo address either.
> Alan Stern
> #syz test: upstream f6e27dbb1afa
"upstream" does not look like a valid git repo address.
> commit 5252eb4c8297fedbf1c5f1e67da44efe00e6ef6b > Author: Pete Zaitcev <zaitcev@kotori.zaitcev.us> > Date: Thu Nov 21 17:24:00 2019 -0600
> usb: Fix a deadlock in usbmon between mmap and read
> Signed-off-by: Pete Zaitcev <zaitcev@redhat.com> > Reported-by: syzbot+56f9673bb4cdcbeb0e92@syzkaller.appspotmail.com
> diff --git a/drivers/usb/mon/mon_bin.c b/drivers/usb/mon/mon_bin.c > index ac2b4fcc265f..f48a23adbc35 100644 > --- a/drivers/usb/mon/mon_bin.c > +++ b/drivers/usb/mon/mon_bin.c > @@ -1039,12 +1039,18 @@ static long mon_bin_ioctl(struct file *file, > unsigned int cmd, unsigned long arg
> mutex_lock(&rp->fetch_lock); > spin_lock_irqsave(&rp->b_lock, flags); > - mon_free_buff(rp->b_vec, rp->b_size/CHUNK_SIZE); > - kfree(rp->b_vec); > - rp->b_vec = vec; > - rp->b_size = size; > - rp->b_read = rp->b_in = rp->b_out = rp->b_cnt = 0; > - rp->cnt_lost = 0; > + if (rp->mmap_active) { > + mon_free_buff(vec, size/CHUNK_SIZE); > + kfree(vec); > + ret = -EBUSY; > + } else { > + mon_free_buff(rp->b_vec, rp->b_size/CHUNK_SIZE); > + kfree(rp->b_vec); > + rp->b_vec = vec; > + rp->b_size = size; > + rp->b_read = rp->b_in = rp->b_out = rp->b_cnt = 0; > + rp->cnt_lost = 0; > + } > spin_unlock_irqrestore(&rp->b_lock, flags); > mutex_unlock(&rp->fetch_lock); > } > @@ -1216,13 +1222,21 @@ mon_bin_poll(struct file *file, struct > poll_table_struct *wait) > static void mon_bin_vma_open(struct vm_area_struct *vma) > { > struct mon_reader_bin *rp = vma->vm_private_data; > + unsigned long flags; > + > + spin_lock_irqsave(&rp->b_lock, flags); > rp->mmap_active++; > + spin_unlock_irqrestore(&rp->b_lock, flags); > }
> static void mon_bin_vma_close(struct vm_area_struct *vma) > { > + unsigned long flags; > + > struct mon_reader_bin *rp = vma->vm_private_data; > + spin_lock_irqsave(&rp->b_lock, flags); > rp->mmap_active--; > + spin_unlock_irqrestore(&rp->b_lock, flags); > }
> /* > @@ -1234,16 +1248,12 @@ static vm_fault_t mon_bin_vma_fault(struct > vm_fault *vmf) > unsigned long offset, chunk_idx; > struct page *pageptr;
> - mutex_lock(&rp->fetch_lock); > offset = vmf->pgoff << PAGE_SHIFT; > - if (offset >= rp->b_size) { > - mutex_unlock(&rp->fetch_lock); > + if (offset >= rp->b_size) > return VM_FAULT_SIGBUS; > - } > chunk_idx = offset / CHUNK_SIZE; > pageptr = rp->b_vec[chunk_idx].pg; > get_page(pageptr); > - mutex_unlock(&rp->fetch_lock); > vmf->page = pageptr; > return 0; > }
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