CVE-2025-68180: drm/amd/display: Fix NULL deref in debugfs odm_combine_segments

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

drm/amd/display: Fix NULL deref in debugfs odmcombinesegments

When a connector is connected but inactive (e.g., disabled by desktop environments), pipectx->streamres.tg will be destroyed. Then, reading odmcombinesegments causes kernel NULL pointer dereference.

BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: errorcode(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 16 UID: 0 PID: 26474 Comm: cat Not tainted 6.17.0+ #2 PREEMPT(lazy) e6a17af9ee6db7c63e9d90dbe5b28ccab67520c6 Hardware name: LENOVO 21Q4/LNVNB161216, BIOS PXCN25WW 03/27/2025 RIP: 0010:odmcombinesegmentsshow+0x93/0xf0 [amdgpu] Code: 41 83 b8 b0 00 00 00 01 75 6e 48 98 ba a1 ff ff ff 48 c1 e0 0c 48 8d 8c 07 d8 02 00 00 48 85 c9 74 2d 48 8b bc 07 f0 08 00 00 <48> 8b 07 48 8b 80 08 02 00> RSP: 0018:ffffd1bf4b953c58 EFLAGS: 00010286 RAX: 0000000000005000 RBX: ffff8e35976b02d0 RCX: ffff8e3aeed052d8 RDX: 00000000ffffffa1 RSI: ffff8e35a3120800 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffff8e3580eb0000 R09: ffff8e35976b02d0 R10: ffffd1bf4b953c78 R11: 0000000000000000 R12: ffffd1bf4b953d08 R13: 0000000000040000 R14: 0000000000000001 R15: 0000000000000001 FS: 00007f44d3f9f740(0000) GS:ffff8e3caa47f000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 00000006485c2000 CR4: 0000000000f50ef0 PKRU: 55555554 Call Trace: <TASK> seqreaditer+0x125/0x490 ? allocfrozenpagesnoprof+0x18f/0x350 seqread+0x12c/0x170 fullproxyread+0x51/0x80 vfsread+0xbc/0x390 ? handlemmfault+0xa46/0xef0 ? dosyscall64+0x71/0x900 ksysread+0x73/0xf0 dosyscall64+0x71/0x900 ? countmemcgevents+0xc2/0x190 ? handlemmfault+0x1d7/0x2d0 ? douseraddrfault+0x21a/0x690 ? excpagefault+0x7e/0x1a0 entrySYSCALL64afterhwframe+0x6c/0x74 RIP: 0033:0x7f44d4031687 Code: 48 89 fa 4c 89 df e8 58 b3 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00> RSP: 002b:00007ffdb4b5f0b0 EFLAGS: 00000202 ORIGRAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007f44d3f9f740 RCX: 00007f44d4031687 RDX: 0000000000040000 RSI: 00007f44d3f5e000 RDI: 0000000000000003 RBP: 0000000000040000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00007f44d3f5e000 R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000040000 </TASK> Modules linked in: tls tcpdiag inetdiag xtmark ccm sndhrtimer sndseqdummy sndseqmidi sndseqoss sndseqmidievent sndrawmidi sndseq sndseqdevice x> sndhdacodecatihdmi sndhdacodecrealteklib lenovowmihelpers thinklmi sndhdacodecgeneric sndhdacodechdmi sndsoccore kvm sndcompress uvcvideo sn> platformprofile joydev amdpmc mousedev machid schfqcodel uinput i2cdev parportpc ppdev lp parport nvmefabrics loop nfnetlink iptables xtables dmcryp> CR2: 0000000000000000 ---[ end trace 0000000000000000 ]--- RIP: 0010:odmcombinesegmentsshow+0x93/0xf0 [amdgpu] Code: 41 83 b8 b0 00 00 00 01 75 6e 48 98 ba a1 ff ff ff 48 c1 e0 0c 48 8d 8c 07 d8 02 00 00 48 85 c9 74 2d 48 8b bc 07 f0 08 00 00 <48> 8b 07 48 8b 80 08 02 00> RSP: 0018:ffffd1bf4b953c58 EFLAGS: 00010286 RAX: 0000000000005000 RBX: ffff8e35976b02d0 RCX: ffff8e3aeed052d8 RDX: 00000000ffffffa1 RSI: ffff8e35a3120800 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffff8e3580eb0000 R09: ffff8e35976b02d0 R10: ffffd1bf4b953c78 R11: 0000000000000000 R12: ffffd1bf4b953d08 R13: 0000000000040000 R14: 0000000000000001 R15: 0000000000000001 FS: 00007f44d3f9f740(0000) GS:ffff8e3caa47f000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 00000006485c2000 CR4: 0000000000f50ef0 PKRU: 55555554

Fix this by checking pipectx-> ---truncated---