CVE-2023-53747

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> vc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF<br /> <br /> After a call to console_unlock() in vcs_write() the vc_data struct can be<br /> freed by vc_port_destruct(). Because of that, the struct vc_data pointer<br /> must be reloaded in the while loop in vcs_write() after console_lock() to<br /> avoid a UAF when vcs_size() is called.<br /> <br /> Syzkaller reported a UAF in vcs_size().<br /> <br /> BUG: KASAN: slab-use-after-free in vcs_size (drivers/tty/vt/vc_screen.c:215)<br /> Read of size 4 at addr ffff8880beab89a8 by task repro_vcs_size/4119<br /> <br /> Call Trace:<br /> <br /> __asan_report_load4_noabort (mm/kasan/report_generic.c:380)<br /> vcs_size (drivers/tty/vt/vc_screen.c:215)<br /> vcs_write (drivers/tty/vt/vc_screen.c:664)<br /> vfs_write (fs/read_write.c:582 fs/read_write.c:564)<br /> ...<br /> <br /> <br /> Allocated by task 1213:<br /> kmalloc_trace (mm/slab_common.c:1064)<br /> vc_allocate (./include/linux/slab.h:559 ./include/linux/slab.h:680<br /> drivers/tty/vt/vt.c:1078 drivers/tty/vt/vt.c:1058)<br /> con_install (drivers/tty/vt/vt.c:3334)<br /> tty_init_dev (drivers/tty/tty_io.c:1303 drivers/tty/tty_io.c:1415<br /> drivers/tty/tty_io.c:1392)<br /> tty_open (drivers/tty/tty_io.c:2082 drivers/tty/tty_io.c:2128)<br /> chrdev_open (fs/char_dev.c:415)<br /> do_dentry_open (fs/open.c:921)<br /> vfs_open (fs/open.c:1052)<br /> ...<br /> <br /> Freed by task 4116:<br /> kfree (mm/slab_common.c:1016)<br /> vc_port_destruct (drivers/tty/vt/vt.c:1044)<br /> tty_port_destructor (drivers/tty/tty_port.c:296)<br /> tty_port_put (drivers/tty/tty_port.c:312)<br /> vt_disallocate_all (drivers/tty/vt/vt_ioctl.c:662 (discriminator 2))<br /> vt_ioctl (drivers/tty/vt/vt_ioctl.c:903)<br /> tty_ioctl (drivers/tty/tty_io.c:2778)<br /> ...<br /> <br /> The buggy address belongs to the object at ffff8880beab8800<br /> which belongs to the cache kmalloc-1k of size 1024<br /> The buggy address is located 424 bytes inside of<br /> freed 1024-byte region [ffff8880beab8800, ffff8880beab8c00)<br /> <br /> The buggy address belongs to the physical page:<br /> page:00000000afc77580 refcount:1 mapcount:0 mapping:0000000000000000<br /> index:0x0 pfn:0xbeab8<br /> head:00000000afc77580 order:3 entire_mapcount:0 nr_pages_mapped:0<br /> pincount:0<br /> flags: 0xfffffc0010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff)<br /> page_type: 0xffffffff()<br /> raw: 000fffffc0010200 ffff888100042dc0 ffffea000426de00 dead000000000002<br /> raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000<br /> page dumped because: kasan: bad access detected<br /> <br /> Memory state around the buggy address:<br /> ffff8880beab8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb<br /> ffff8880beab8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb<br /> &gt;ffff8880beab8980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb<br /> ^<br /> ffff8880beab8a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb<br /> ffff8880beab8a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb<br /> ==================================================================<br /> Disabling lock debugging due to kernel taint