Size of kmalloc() in vc_do_resize() is controlled by user. Too large kmalloc() size triggers WARNING message on console. Put a reasonable upper bound on terminal size to prevent WARNINGs.
Signed-off-by: Dmitry Vyukov <dvyu...@google.com> CC: David Rientjes <rient...@google.com> Cc: One Thousand Gnomes <gno...@lxorguk.ukuu.org.uk> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> Cc: Jiri Slaby <jsl...@suse.com> Cc: Peter Hurley <pe...@hurleysoftware.com> Cc: linux-kernel@vger.kernel.org Cc: syzkal...@googlegroups.com --- I've sent a patch that adds __GFP_NOWARN to the kmalloc() a while ago: https://groups.google.com/d/msg/syzkaller/9xTEI2ghFwA/fTgt7oonAAAJ But David and One Thousand Gnomes suggested that we should put a reasonable upper bound rather than blindly trying kmalloc(). "I think we can go down to something like cols * lines < 4MB with complete safety". Example WARNING: WARNING: CPU: 3 PID: 7642 at mm/page_alloc.c:2999 __alloc_pages_nodemask+0x7d2/0x1760() Modules linked in: CPU: 3 PID: 7642 Comm: a.out Not tainted 4.4.0+ #276 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 00000000ffffffff ffff88006d24f610 ffffffff82999e2d 0000000000000000 ffff880060d9af80 ffffffff86475560 ffff88006d24f650 ffffffff81352089 ffffffff816721e2 ffffffff86475560 0000000000000bb7 00000000024240c0 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [<ffffffff82999e2d>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50 [<ffffffff81352089>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:482 [<ffffffff813522b9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:515 [< inline >] __alloc_pages_slowpath mm/page_alloc.c:2999 [<ffffffff816721e2>] __alloc_pages_nodemask+0x7d2/0x1760 mm/page_alloc.c:3253 [<ffffffff8174a799>] alloc_pages_current+0xe9/0x450 mm/mempolicy.c:2090 [< inline >] alloc_pages include/linux/gfp.h:459 [<ffffffff8166df66>] alloc_kmem_pages+0x16/0x100 mm/page_alloc.c:3433 [<ffffffff816c698f>] kmalloc_order+0x1f/0x80 mm/slab_common.c:1008 [<ffffffff816c6a0f>] kmalloc_order_trace+0x1f/0x140 mm/slab_common.c:1019 [< inline >] kmalloc_large include/linux/slab.h:395 [<ffffffff8175b624>] __kmalloc+0x2f4/0x340 mm/slub.c:3557 [< inline >] kmalloc include/linux/slab.h:468 [<ffffffff82d47800>] vc_do_resize+0x2c0/0x1140 drivers/tty/vt/vt.c:874 [<ffffffff82d4878a>] vt_resize+0xaa/0xe0 drivers/tty/vt/vt.c:993 [< inline >] tiocswinsz drivers/tty/tty_io.c:2357 [<ffffffff82cf22b3>] tty_ioctl+0x1083/0x2160 drivers/tty/tty_io.c:2869 [< inline >] vfs_ioctl fs/ioctl.c:43 [<ffffffff817efdac>] do_vfs_ioctl+0x18c/0xfb0 fs/ioctl.c:674 [< inline >] SYSC_ioctl fs/ioctl.c:689 [<ffffffff817f0c5f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:680 --- drivers/tty/vt/vt.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 06fb39c..652abc1 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -870,6 +870,8 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc, if (new_cols == vc->vc_cols && new_rows == vc->vc_rows) return 0; + if (new_screen_size > (4 << 20)) + return -EINVAL; newscreen = kmalloc(new_screen_size, GFP_USER); if (!newscreen) return -ENOMEM; -- 2.8.0.rc3.226.g39d4020
