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George Kennedy 8fb9ea65c9 vc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF 
After a call to console_unlock() in vcs_write() the vc_data struct can be
freed by vc_port_destruct(). Because of that, the struct vc_data pointer
must be reloaded in the while loop in vcs_write() after console_lock() to
avoid a UAF when vcs_size() is called.

Syzkaller reported a UAF in vcs_size().

BUG: KASAN: slab-use-after-free in vcs_size (drivers/tty/vt/vc_screen.c:215)
Read of size 4 at addr ffff8880beab89a8 by task repro_vcs_size/4119

Call Trace:
 <TASK>
__asan_report_load4_noabort (mm/kasan/report_generic.c:380)
vcs_size (drivers/tty/vt/vc_screen.c:215)
vcs_write (drivers/tty/vt/vc_screen.c:664)
vfs_write (fs/read_write.c:582 fs/read_write.c:564)
...
 <TASK>

Allocated by task 1213:
kmalloc_trace (mm/slab_common.c:1064)
vc_allocate (./include/linux/slab.h:559 ./include/linux/slab.h:680
    drivers/tty/vt/vt.c:1078 drivers/tty/vt/vt.c:1058)
con_install (drivers/tty/vt/vt.c:3334)
tty_init_dev (drivers/tty/tty_io.c:1303 drivers/tty/tty_io.c:1415
    drivers/tty/tty_io.c:1392)
tty_open (drivers/tty/tty_io.c:2082 drivers/tty/tty_io.c:2128)
chrdev_open (fs/char_dev.c:415)
do_dentry_open (fs/open.c:921)
vfs_open (fs/open.c:1052)
...

Freed by task 4116:
kfree (mm/slab_common.c:1016)
vc_port_destruct (drivers/tty/vt/vt.c:1044)
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:2778)
...

The buggy address belongs to the object at ffff8880beab8800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 424 bytes inside of
 freed 1024-byte region [ffff8880beab8800, ffff8880beab8c00)

The buggy address belongs to the physical page:
page:00000000afc77580 refcount:1 mapcount:0 mapping:0000000000000000
    index:0x0 pfn:0xbeab8
head:00000000afc77580 order:3 entire_mapcount:0 nr_pages_mapped:0
    pincount:0
flags: 0xfffffc0010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff)
page_type: 0xffffffff()
raw: 000fffffc0010200 ffff888100042dc0 ffffea000426de00 dead000000000002
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880beab8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880beab8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880beab8980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8880beab8a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880beab8a80: 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()")
Cc: stable <stable@kernel.org>
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: George Kennedy <george.kennedy@oracle.com>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/1683889728-10411-1-git-send-email-george.kennedy@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2023-05-13 20:01:13 +09:00
..
hvc xen: branch for v6.3-rc4 2023-03-24 09:44:43 -07:00
ipwireless
…
serdev serdev: Add method to assert break signal over tty UART port 2023-04-23 21:51:25 -07:00
serial serial: qcom-geni: fix enabling deactivated interrupt 2023-05-13 20:00:54 +09:00
vt vc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF 2023-05-13 20:01:13 +09:00
Kconfig Char/Misc drivers for 6.4-rc1 2023-04-27 12:07:50 -07:00
Makefile
…
amiserial.c tty: Convert hw_stopped in tty_struct to bool 2023-03-17 15:01:09 +01:00
ehv_bytechan.c tty: evh_bytechan: Replace NO_IRQ by 0 2022-11-02 08:10:42 +01:00
goldfish.c
…
mips_ejtag_fdc.c
…
moxa.c tty: moxa: Rename dtr/rts parameters/variables to active 2023-01-19 16:04:35 +01:00
mxser.c tty: Convert hw_stopped in tty_struct to bool 2023-03-17 15:01:09 +01:00
n_gsm.c n_gsm: Use array_index_nospec() with index that comes from userspace 2023-04-20 14:11:33 +02:00
n_hdlc.c
…
n_null.c
…
n_tty.c n_tty: Reindent if condition 2023-03-17 15:01:09 +01:00
nozomi.c
…
pty.c tty: make tty_class a static const structure 2023-04-03 21:43:07 +02:00
rpmsg_tty.c
…
synclink_gt.c tty: synclink_gt: don't allocate and pass dummy flags 2023-04-20 13:32:53 +02:00
sysrq.c treewide: Convert del_timer*() to timer_shutdown*() 2022-12-25 13:38:09 -08:00
tty.h tty: Prevent writing chars during tcsetattr TCSADRAIN/FLUSH 2023-03-29 10:55:53 +02:00
tty_audit.c
…
tty_baudrate.c
…
tty_buffer.c tty: Convert tty_buffer flags to bool 2022-11-09 13:02:16 +01:00
tty_io.c Driver core changes for 6.4-rc1 2023-04-27 11:53:57 -07:00
tty_ioctl.c tty: Prevent writing chars during tcsetattr TCSADRAIN/FLUSH 2023-03-29 10:55:53 +02:00
tty_jobctrl.c
…
tty_ldisc.c tty: tty_ldisc: Remove the ret variable 2023-03-09 17:11:18 +01:00
tty_ldsem.c
…
tty_mutex.c
…
tty_port.c tty: Convert ->dtr_rts() to take bool argument 2023-01-19 16:04:35 +01:00
ttynull.c
…
vcc.c
…