CVE-2026-31765: drm/amdgpu: Change AMDGPU_VA_RESERVED_TRAP_SIZE to 64KB

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

drm/amdgpu: Change AMDGPUVARESERVEDTRAPSIZE to 64KB

Currently, AMDGPUVARESERVEDTRAPSIZE is hardcoded to 8KB, while KFDCWSRTBATMASIZE is defined as 2 PAGESIZE. On systems with 4K pages, both values match (8KB), so allocation and reserved space are consistent.

However, on 64K page-size systems, KFDCWSRTBATMASIZE becomes 128KB, while the reserved trap area remains 8KB. This mismatch causes the kernel to crash when running rocminfo or rccl unit tests.

Kernel attempted to read user page (2) - exploit attempt? (uid: 1001) BUG: Kernel NULL pointer dereference on read at 0x00000002 Faulting instruction address: 0xc0000000002c8a64 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGESIZE=64K MMU=Radix SMP NRCPUS=2048 NUMA pSeries CPU: 34 UID: 1001 PID: 9379 Comm: rocminfo Tainted: G E 6.19.0-rc4-amdgpu-00320-gf23176405700 #56 VOLUNTARY Tainted: [E]=UNSIGNEDMODULE Hardware name: IBM,9105-42A POWER10 (architected) 0x800200 0xf000006 of:IBM,FW1060.30 (ML1060896) hv:phyp pSeries NIP: c0000000002c8a64 LR: c00000000125dbc8 CTR: c00000000125e730 REGS: c0000001e0957580 TRAP: 0300 Tainted: G E MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 24008268 XER: 00000036 CFAR: c00000000125dbc4 DAR: 0000000000000002 DSISR: 40000000 IRQMASK: 1 GPR00: c00000000125d908 c0000001e0957820 c0000000016e8100 c00000013d814540 GPR04: 0000000000000002 c00000013d814550 0000000000000045 0000000000000000 GPR08: c00000013444d000 c00000013d814538 c00000013d814538 0000000084002268 GPR12: c00000000125e730 c000007e2ffd5f00 ffffffffffffffff 0000000000020000 GPR16: 0000000000000000 0000000000000002 c00000015f653000 0000000000000000 GPR20: c000000138662400 c00000013d814540 0000000000000000 c00000013d814500 GPR24: 0000000000000000 0000000000000002 c0000001e0957888 c0000001e0957878 GPR28: c00000013d814548 0000000000000000 c00000013d814540 c0000001e0957888 NIP [c0000000002c8a64] mutexaddwaiter+0x24/0xc0 LR [c00000000125dbc8] mutexlock.constprop.0+0x318/0xd00 Call Trace: 0xc0000001e0957890 (unreliable) mutexlock.constprop.0+0x58/0xd00 amdgpuamdkfdgpuvmallocmemoryofgpu+0x6fc/0xb60 [amdgpu] kfdprocessallocgpuvm+0x54/0x1f0 [amdgpu] kfdprocessdeviceinitcwsrdgpu+0xa4/0x1a0 [amdgpu] kfdprocessdeviceinitvm+0xd8/0x2e0 [amdgpu] kfdioctlacquirevm+0xd0/0x130 [amdgpu] kfdioctl+0x514/0x670 [amdgpu] sysioctl+0x134/0x180 systemcallexception+0x114/0x300 systemcallvectoredcommon+0x15c/0x2ec

This patch changes AMDGPUVARESERVEDTRAPSIZE to 64 KB and KFDCWSRTBATMASIZE to the AMD GPU page size. This means we reserve 64 KB for the trap in the address space, but only allocate 8 KB within it. With this approach, the allocation size never exceeds the reserved area.

(cherry picked from commit 31b8de5e55666f26ea7ece5f412b83eab3f56dbb)