On 03/18/2015 01:30 AM, Konstantin Khlebnikov wrote: > + /* > + * Read-only SUID/SGID binares are mapped as copy-on-read > + * this protects them against exploiting with Rowhammer. > + */ > + if (!(file->f_mode & FMODE_WRITE) && > + ((inode->i_mode & S_ISUID) || ((inode->i_mode & S_ISGID) && > + (inode->i_mode & S_IXGRP)))) { > + vm_flags &= ~(VM_SHARED | VM_MAYSHARE); > + vm_flags |= VM_COR; > + } I think we probably need to come to _some_ sort of understanding in the kernel of how much we are willing to do to thwart these kinds of attacks. I suspect it's a very deep rabbit hole. For this particular case, I don't see how this would be effective. The existing exploit which you reference attacks PTE pages which are unmapped in to the user address space. I'm confused how avoiding mapping a page in to an attacker's process can keep it from being exploited. Right now, there's a relatively small number of pages that will get COW'd for a SUID binary. This greatly increases the number which could allow spraying of these (valuable) copy-on-read pages. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>