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USB: fix usbmon BUG trigger

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commit 46eb14a6e1 upstream.

Automated tests triggered this by opening usbmon and accessing the
mmap while simultaneously resizing the buffers. This bug was with
us since 2006, because typically applications only size the buffers
once and thus avoid racing. Reported by Kirill A. Shutemov.

Reported-by: <syzbot+f9831b881b3e849829fc@syzkaller.appspotmail.com>
Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Pete Zaitcev 2018-01-08 15:46:41 -06:00 committed by Ben Hutchings
parent 84f7438d82
commit d1168c1357
1 changed files with 7 additions and 1 deletions
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8
drivers/usb/mon/mon_bin.c
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@ -1000,7 +1000,9 @@ static long mon_bin_ioctl(struct file *file, unsigned int cmd, unsigned long arg
break;
case MON_IOCQ_RING_SIZE:
mutex_lock(&rp->fetch_lock);
ret = rp->b_size;
mutex_unlock(&rp->fetch_lock);
break;
case MON_IOCT_RING_SIZE:
@ -1227,12 +1229,16 @@ static int mon_bin_vma_fault(struct vm_area_struct *vma, 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)
if (offset >= rp->b_size) {
mutex_unlock(&rp->fetch_lock);
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;
}