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George Kennedy 8506f16aae vc_screen: move load of struct vc_data pointer in vcs_read() to avoid UAF 
[ Upstream commit 226fae124b ]

After a call to console_unlock() in vcs_read() the vc_data struct can be
freed by vc_deallocate(). Because of that, the struct vc_data pointer
load must be done at the top of while loop in vcs_read() to avoid a UAF
when vcs_size() is called.

Syzkaller reported a UAF in vcs_size().

BUG: KASAN: use-after-free in vcs_size (drivers/tty/vt/vc_screen.c:215)
Read of size 4 at addr ffff8881137479a8 by task 4a005ed81e27e65/1537

CPU: 0 PID: 1537 Comm: 4a005ed81e27e65 Not tainted 6.2.0-rc5 #1
Hardware name: Red Hat KVM, BIOS 1.15.0-2.module
Call Trace:
  <TASK>
__asan_report_load4_noabort (mm/kasan/report_generic.c:350)
vcs_size (drivers/tty/vt/vc_screen.c:215)
vcs_read (drivers/tty/vt/vc_screen.c:415)
vfs_read (fs/read_write.c:468 fs/read_write.c:450)
...
  </TASK>

Allocated by task 1191:
...
kmalloc_trace (mm/slab_common.c:1069)
vc_allocate (./include/linux/slab.h:580 ./include/linux/slab.h:720
     drivers/tty/vt/vt.c:1128 drivers/tty/vt/vt.c:1108)
con_install (drivers/tty/vt/vt.c:3383)
tty_init_dev (drivers/tty/tty_io.c:1301 drivers/tty/tty_io.c:1413
     drivers/tty/tty_io.c:1390)
tty_open (drivers/tty/tty_io.c:2080 drivers/tty/tty_io.c:2126)
chrdev_open (fs/char_dev.c:415)
do_dentry_open (fs/open.c:883)
vfs_open (fs/open.c:1014)
...

Freed by task 1548:
...
kfree (mm/slab_common.c:1021)
vc_port_destruct (drivers/tty/vt/vt.c:1094)
tty_port_destructor (drivers/tty/tty_port.c:296)
tty_port_put (drivers/tty/tty_port.c:312)
vt_disallocate_all (drivers/tty/vt/vt_ioctl.c:662 (discriminator 2))
vt_ioctl (drivers/tty/vt/vt_ioctl.c:903)
tty_ioctl (drivers/tty/tty_io.c:2776)
...

The buggy address belongs to the object at ffff888113747800
  which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 424 bytes inside of
  1024-byte region [ffff888113747800, ffff888113747c00)

The buggy address belongs to the physical page:
page:00000000b3fe6c7c refcount:1 mapcount:0 mapping:0000000000000000
     index:0x0 pfn:0x113740
head:00000000b3fe6c7c order:3 compound_mapcount:0 subpages_mapcount:0
     compound_pincount:0
anon flags: 0x17ffffc0010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff)
raw: 0017ffffc0010200 ffff888100042dc0 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff888113747880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff888113747900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff888113747980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                   ^
  ffff888113747a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff888113747a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Disabling lock debugging due to kernel taint

Fixes: ac751efa6a ("console: rename acquire/release_console_sem() to console_lock/unlock()")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Suggested-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: George Kennedy <george.kennedy@oracle.com>
Link: https://lore.kernel.org/r/1674577014-12374-1-git-send-email-george.kennedy@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2023-02-09 11:28:14 +01:00
..
hvc hvc/xen: lock console list traversal 2023-01-18 11:58:26 +01:00
ipwireless
…
serdev
…
serial serial: exar: Add support for Sealevel 7xxxC serial cards 2023-01-24 07:24:39 +01:00
vt vc_screen: move load of struct vc_data pointer in vcs_read() to avoid UAF 2023-02-09 11:28:14 +01:00
Kconfig
…
Makefile
…
amiserial.c
…
ehv_bytechan.c
…
goldfish.c
…
mips_ejtag_fdc.c
…
moxa.c
…
mxser.c tty: mxser: remove redundant assignment to hwid 2022-09-01 17:59:36 +02:00
n_gsm.c tty: n_gsm: fix sleep-in-atomic-context bug in gsm_control_send 2022-11-03 04:12:09 +01:00
n_hdlc.c tty: n_hdlc: remove HDLC_MAGIC 2022-09-22 16:12:34 +02:00
n_null.c
…
n_tty.c
…
nozomi.c
…
pty.c
…
rpmsg_tty.c
…
synclink_gt.c tty: synclink_gt: remove MGSL_MAGIC 2022-09-22 16:12:34 +02:00
sysrq.c
…
tty.h
…
tty_audit.c
…
tty_baudrate.c
…
tty_buffer.c tty: Fix lookahead_buf crash with serdev 2022-08-30 14:31:53 +02:00
tty_io.c tty: remove TTY_DRIVER_MAGIC 2022-09-22 16:12:34 +02:00
tty_ioctl.c termios: start unifying non-UAPI parts of asm/termios.h 2022-09-09 10:44:34 +02:00
tty_jobctrl.c
…
tty_ldisc.c
…
tty_ldsem.c
…
tty_mutex.c tty: remove TTY_MAGIC 2022-09-22 16:12:34 +02:00
tty_port.c
…
ttynull.c
…
vcc.c termios: start unifying non-UAPI parts of asm/termios.h 2022-09-09 10:44:34 +02:00