CVE-2023-52648: NULL Pointer Dereference

In the Linux kernel, the following vulnerability has been resolved:

drm/vmwgfx: Unmap the surface before resetting it on a plane state

Switch to a new plane state requires unreferencing of all held surfaces. In the work required for mob cursors the mapped surfaces started being cached but the variable indicating whether the surface is currently mapped was not being reset. This leads to crashes as the duplicated state, incorrectly, indicates the that surface is mapped even when no surface is present. That's because after unreferencing the surface it's perfectly possible for the plane to be backed by a bo instead of a surface.

Reset the surface mapped flag when unreferencing the plane state surface to fix null derefs in cleanup. Fixes crashes in KDE KWin 6.0 on Wayland:

Oops: 0000 [#1] PREEMPT SMP PTI CPU: 4 PID: 2533 Comm: kwin_wayland Not tainted 6.7.0-rc3-vmwgfx #2 Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020 RIP: 0010:vmw_du_cursor_plane_cleanup_fb+0x124/0x140 [vmwgfx] Code: 00 00 00 75 3a 48 83 c4 10 5b 5d c3 cc cc cc cc 48 8b b3 a8 00 00 00 48 c7 c7 99 90 43 c0 e8 93 c5 db ca 48 8b 83 a8 00 00 00 <48> 8b 78 28 e8 e3 f> RSP: 0018:ffffb6b98216fa80 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff969d84cdcb00 RCX: 0000000000000027 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff969e75f21600 RBP: ffff969d4143dc50 R08: 0000000000000000 R09: ffffb6b98216f920 R10: 0000000000000003 R11: ffff969e7feb3b10 R12: 0000000000000000 R13: 0000000000000000 R14: 000000000000027b R15: ffff969d49c9fc00 FS: 00007f1e8f1b4180(0000) GS:ffff969e75f00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000028 CR3: 0000000104006004 CR4: 00000000003706f0 Call Trace: <TASK> ? __die+0x23/0x70 ? page_fault_oops+0x171/0x4e0 ? exc_page_fault+0x7f/0x180 ? asm_exc_page_fault+0x26/0x30 ? vmw_du_cursor_plane_cleanup_fb+0x124/0x140 [vmwgfx] drm_atomic_helper_cleanup_planes+0x9b/0xc0 commit_tail+0xd1/0x130 drm_atomic_helper_commit+0x11a/0x140 drm_atomic_commit+0x97/0xd0 ? __pfx___drm_printfn_info+0x10/0x10 drm_atomic_helper_update_plane+0xf5/0x160 drm_mode_cursor_universal+0x10e/0x270 drm_mode_cursor_common+0x102/0x230 ? __pfx_drm_mode_cursor2_ioctl+0x10/0x10 drm_ioctl_kernel+0xb2/0x110 drm_ioctl+0x26d/0x4b0 ? __pfx_drm_mode_cursor2_ioctl+0x10/0x10 ? __pfx_drm_ioctl+0x10/0x10 vmw_generic_ioctl+0xa4/0x110 [vmwgfx] __x64_sys_ioctl+0x94/0xd0 do_syscall_64+0x61/0xe0 ? __x64_sys_ioctl+0xaf/0xd0 ? syscall_exit_to_user_mode+0x2b/0x40 ? do_syscall_64+0x70/0xe0 ? __x64_sys_ioctl+0xaf/0xd0 ? syscall_exit_to_user_mode+0x2b/0x40 ? do_syscall_64+0x70/0xe0 ? exc_page_fault+0x7f/0x180 entry_SYSCALL_64_after_hwframe+0x6e/0x76 RIP: 0033:0x7f1e93f279ed Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff f> RSP: 002b:00007ffca0faf600 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000055db876ed2c0 RCX: 00007f1e93f279ed RDX: 00007ffca0faf6c0 RSI: 00000000c02464bb RDI: 0000000000000015 RBP: 00007ffca0faf650 R08: 000055db87184010 R09: 0000000000000007 R10: 000055db886471a0 R11: 0000000000000246 R12: 00007ffca0faf6c0 R13: 00000000c02464bb R14: 0000000000000015 R15: 00007ffca0faf790 </TASK> Modules linked in: snd_seq_dummy snd_hrtimer nf_conntrack_netbios_ns nf_conntrack_broadcast nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_ine> CR2: 0000000000000028 ---[ end trace 0000000000000000 ]--- RIP: 0010:vmw_du_cursor_plane_cleanup_fb+0x124/0x140 [vmwgfx] Code: 00 00 00 75 3a 48 83 c4 10 5b 5d c3 cc cc cc cc 48 8b b3 a8 00 00 00 48 c7 c7 99 90 43 c0 e8 93 c5 db ca 48 8b 83 a8 00 00 00 <48> 8b 78 28 e8 e3 f> RSP: 0018:ffffb6b98216fa80 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff969d84cdcb00 RCX: 0000000000000027 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff969e75f21600 RBP: ffff969d4143 ---truncated---