dm-verity: restart or panic on an I/O error

commit e6a3531dd542cb127c8de32ab1e54a48ae19962b upstream.

Maxim Suhanov reported that dm-verity doesn't crash if an I/O error
happens. In theory, this could be used to subvert security, because an
attacker can create sectors that return error with the Write Uncorrectable
command. Some programs may misbehave if they have to deal with EIO.

This commit fixes dm-verity, so that if "panic_on_corruption" or
"restart_on_corruption" was specified and an I/O error happens, the
machine will panic or restart.

This commit also changes kernel_restart to emergency_restart -
kernel_restart calls reboot notifiers and these reboot notifiers may wait
for the bio that failed. emergency_restart doesn't call the notifiers.

Reported-by: Maxim Suhanov <dfirblog@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 431a61e1a8b7b8fd8058d9a43c209d98c31a49d1..b859c43ae1c699071c95491a6283f65d8a9a19c4 100644 (file)
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -265,8 +265,10 @@ out:
        if (v->mode == DM_VERITY_MODE_LOGGING)
                return 0;
 
-       if (v->mode == DM_VERITY_MODE_RESTART)
-               kernel_restart("dm-verity device corrupted");
+       if (v->mode == DM_VERITY_MODE_RESTART) {
+               pr_emerg("dm-verity device corrupted\n");
+               emergency_restart();
+       }
 
        if (v->mode == DM_VERITY_MODE_PANIC)
                panic("dm-verity device corrupted");
@@ -691,6 +693,23 @@ static void verity_finish_io(struct dm_verity_io *io, blk_status_t status)
        if (!static_branch_unlikely(&use_bh_wq_enabled) || !io->in_bh)
                verity_fec_finish_io(io);
 
+       if (unlikely(status != BLK_STS_OK) &&
+           unlikely(!(bio->bi_opf & REQ_RAHEAD)) &&
+           !verity_is_system_shutting_down()) {
+               if (v->mode == DM_VERITY_MODE_RESTART ||
+                   v->mode == DM_VERITY_MODE_PANIC)
+                       DMERR_LIMIT("%s has error: %s", v->data_dev->name,
+                                       blk_status_to_str(status));
+
+               if (v->mode == DM_VERITY_MODE_RESTART) {
+                       pr_emerg("dm-verity device corrupted\n");
+                       emergency_restart();
+               }
+
+               if (v->mode == DM_VERITY_MODE_PANIC)
+                       panic("dm-verity device corrupted");
+       }
+
        bio_endio(bio);
 }