On 03/10/2015 12:11 AM, Kirill A. Shutemov wrote: > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > > As pointed by recent post[1] on exploiting DRAM physical imperfection, > /proc/PID/pagemap exposes sensitive information which can be used to do > attacks. > > This is RFC patch which disallow anybody without CAP_SYS_ADMIN to read > the pagemap. > > Any comments? If I'm not mistaken, the pagemap file is used by some userspace that does working-set size analysis. But this thing only needs the flags (referenced bit) from the PTE-s. Maybe it would be better not to lock this file completely, but instead report the PFN part as zero? Other than this, I don't mind :) Although we use this heavily in CRIU we anyway work only with the CAP_SYS_ADMIN, so adding the new one doesn't hurt. Thanks, Pavel > [1] http://googleprojectzero.blogspot.com/2015/03/exploiting-dram-rowhammer-bug-to-gain.html > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Cc: Mark Seaborn <mseaborn@xxxxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > --- > fs/proc/task_mmu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 246eae84b13b..b72b36e64286 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -1322,6 +1322,9 @@ out: > > static int pagemap_open(struct inode *inode, struct file *file) > { > + /* do not disclose physical addresses: attack vector */ > + if (!capable(CAP_SYS_ADMIN)) > + return -EPERM; > pr_warn_once("Bits 55-60 of /proc/PID/pagemap entries are about " > "to stop being page-shift some time soon. See the " > "linux/Documentation/vm/pagemap.txt for details.\n"); > -- 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>