wireguard-linux/drivers/tty/vt/vt.c, branch jd/unified-crypt-queue

vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console

2020-03-27T11:35:04Z

The VT_DISALLOCATE ioctl can free a virtual console while tty_release() is still running, causing a use-after-free in con_shutdown(). This occurs because VT_DISALLOCATE considers a virtual console's 'struct vc_data' to be unused as soon as the corresponding tty's refcount hits 0. But actually it may be still being closed. Fix this by making vc_data be reference-counted via the embedded 'struct tty_port'. A newly allocated virtual console has refcount 1. Opening it for the first time increments the refcount to 2. Closing it for the last time decrements the refcount (in tty_operations::cleanup() so that it happens late enough), as does VT_DISALLOCATE. Reproducer: #include #include #include #include int main() { if (fork()) { for (;;) close(open("/dev/tty5", O_RDWR)); } else { int fd = open("/dev/tty10", O_RDWR); for (;;) ioctl(fd, VT_DISALLOCATE, 5); } } KASAN report: BUG: KASAN: use-after-free in con_shutdown+0x76/0x80 drivers/tty/vt/vt.c:3278 Write of size 8 at addr ffff88806a4ec108 by task syz_vt/129 CPU: 0 PID: 129 Comm: syz_vt Not tainted 5.6.0-rc2 #11 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20191223_100556-anatol 04/01/2014 Call Trace: [...] con_shutdown+0x76/0x80 drivers/tty/vt/vt.c:3278 release_tty+0xa8/0x410 drivers/tty/tty_io.c:1514 tty_release_struct+0x34/0x50 drivers/tty/tty_io.c:1629 tty_release+0x984/0xed0 drivers/tty/tty_io.c:1789 [...] Allocated by task 129: [...] kzalloc include/linux/slab.h:669 [inline] vc_allocate drivers/tty/vt/vt.c:1085 [inline] vc_allocate+0x1ac/0x680 drivers/tty/vt/vt.c:1066 con_install+0x4d/0x3f0 drivers/tty/vt/vt.c:3229 tty_driver_install_tty drivers/tty/tty_io.c:1228 [inline] tty_init_dev+0x94/0x350 drivers/tty/tty_io.c:1341 tty_open_by_driver drivers/tty/tty_io.c:1987 [inline] tty_open+0x3ca/0xb30 drivers/tty/tty_io.c:2035 [...] Freed by task 130: [...] kfree+0xbf/0x1e0 mm/slab.c:3757 vt_disallocate drivers/tty/vt/vt_ioctl.c:300 [inline] vt_ioctl+0x16dc/0x1e30 drivers/tty/vt/vt_ioctl.c:818 tty_ioctl+0x9db/0x11b0 drivers/tty/tty_io.c:2660 [...] Fixes: 4001d7b7fc27 ("vt: push down the tty lock so we can see what is left to tackle") Cc: # v3.4+ Reported-by: syzbot+522643ab5729b0421998@syzkaller.appspotmail.com Acked-by: Jiri Slaby Signed-off-by: Eric Biggers Link: https://lore.kernel.org/r/20200322034305.210082-2-ebiggers@kernel.org Signed-off-by: Greg Kroah-Hartman

vt: indent switch-case in setterm_command properly

2020-03-16T07:41:17Z

Shift cases one level left. This makes the code more readable and some lines need not wrap anymore. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20200316065911.11024-3-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

vt: use min() to limit intervals

2020-03-16T07:41:17Z

Instead of awkward ternary operator with comparison, use simple min() for blankinterval and vesa_off_interval. No functional change intended and "objdump -d" proves that. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20200316065911.11024-1-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

vt: drop redundant might_sleep() in do_con_write()

2020-03-12T16:36:10Z

The might_sleep() in do_con_write() is redundant because console_lock() already contains might_sleep(). Remove it. Signed-off-by: Eric Biggers Link: https://lore.kernel.org/r/20200224073450.292892-1-ebiggers@kernel.org Signed-off-by: Greg Kroah-Hartman

Merge 5.6-rc5 into tty-next

2020-03-10T09:02:49Z

We need the vt fixes in here and it resolves a merge issue with drivers/tty/vt/selection.c Reported-by: Stephen Rothwell Signed-off-by: Greg Kroah-Hartman

vt: selection, push console lock down

2020-02-28T15:06:49Z

We need to nest the console lock in sel_lock, so we have to push it down a bit. Fortunately, the callers of set_selection_* just lock the console lock around the function call. So moving it down is easy. In the next patch, we switch the order. Signed-off-by: Jiri Slaby Fixes: 07e6124a1a46 ("vt: selection, close sel_buffer race") Cc: stable Link: https://lore.kernel.org/r/20200228115406.5735-1-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

Merge 5.6-rc3 into tty-next

2020-02-24T07:39:55Z

We want the tty fixes in here as well. Signed-off-by: Greg Kroah-Hartman

vt: selection, introduce vc_is_sel

2020-02-21T09:31:18Z

Avoid global variables (namely sel_cons) by introducing vc_is_sel. It checks whether the parameter is the current selection console. This will help putting sel_cons to a struct later. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20200219073951.16151-1-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

vt: fix scrollback flushing on background consoles

2020-02-10T21:51:44Z

Commit a6dbe4427559 ("vt: perform safe console erase in the right order") provided fixes to an earlier commit by gathering all console scrollback flushing operations in a function of its own. This includes the invocation of vc_sw->con_switch() as previously done through a update_screen() call. That commit failed to carry over the con_is_visible() conditional though, as well as cursor handling, which caused problems when "\e[3J" was written to a background console. One could argue for preserving the call to update_screen(). However this does far more than we need, and it is best to remove scrollback assumptions from it. Instead let's gather the minimum needed to actually perform scrollback flushing properly in that one place. While at it, let's document the vc_sw->con_switch() side effect being relied upon. Signed-off-by: Nicolas Pitre Reported-and-tested-by: Lukas Wunner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/nycvar.YSQ.7.76.2001281205560.1655@knanqh.ubzr Signed-off-by: Greg Kroah-Hartman

vt: Correct comment documenting do_take_over_console()

2020-01-14T15:00:54Z

Commit 3e795de7631b ("[PATCH] VT binding: Add binding/unbinding support for the VT console") introduced a code comment claiming that "do_take_over_console is basically a register followed by unbind". However the function actually performs a register followed by *bind*. Signed-off-by: Lukas Wunner Cc: Antonino A. Daplas Link: https://lore.kernel.org/r/a500f005ba7013ca8165a6d42f59b2183d56114f.1578574427.git.lukas@wunner.de Signed-off-by: Greg Kroah-Hartman