4.4-stable review patch. If anyone has any objections, please let me know.
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From: Pete Zaitcev zaitcev@redhat.com
commit 46eb14a6e1585d99c1b9f58d0e7389082a5f466b 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
--- drivers/usb/mon/mon_bin.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
--- a/drivers/usb/mon/mon_bin.c +++ b/drivers/usb/mon/mon_bin.c @@ -1001,7 +1001,9 @@ static long mon_bin_ioctl(struct file *f 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: @@ -1228,12 +1230,16 @@ static int mon_bin_vma_fault(struct vm_a 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; }