drm/amdkfd: Fix OOB memory exposure in get_wave_state()

The get_wave_state() function for v9 trusts cp_hqd_cntl_stack_size and
cp_hqd_cntl_stack_offset values read directly from the MQD, which are
written by GPU microcode and fully attacker-controlled on the
CRIU-restore path (via AMDKFD_IOC_RESTORE_PROCESS with H3).

this leads to an unbounded copy_to_user() that can leak adjacent
GTT/kernel memory. If offset > size, integer underflow produces a ~4 GiB
read length, if size is set to 1 MiB against a 4 KiB allocation, we leak
1 MiB of adjacent kernel memory (other queues' MQDs, ring buffers, KASLR
pointers).

Fix by clamping both cp_hqd_cntl_stack_size to the actual allocated
buffer size (q->ctl_stack_size) and cp_hqd_cntl_stack_offset to the
clamped size before performing arithmetic and copy_to_user().

This ensures we never read beyond the allocated kernel BO regardless of
attacker-supplied MQD field values.

Signed-off-by: Sunday Clement <Sunday.Clement@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
index 56a7679ca98d57b7642a03197fa9596e53af84b2..17bfb419b2020a8f86099f6d8e2fbf8167d4d0c6 100644 (file)
--- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
@@ -375,11 +375,15 @@ static int get_wave_state(struct mqd_manager *mm, void *mqd,
 {
        struct v9_mqd *m;
        struct kfd_context_save_area_header header;
+       u32 cntl_stack_size;
+       u32 cntl_stack_offset;
 
        /* Control stack is located one page after MQD. */
        void *mqd_ctl_stack = (void *)((uintptr_t)mqd + AMDGPU_GPU_PAGE_SIZE);
 
        m = get_mqd(mqd);
+       cntl_stack_size = min_t(u32, m->cp_hqd_cntl_stack_size,   q->ctl_stack_size);
+       cntl_stack_offset = min_t(u32, m->cp_hqd_cntl_stack_offset, cntl_stack_size);
 
        *ctl_stack_used_size = m->cp_hqd_cntl_stack_size -
                m->cp_hqd_cntl_stack_offset;
@@ -395,9 +399,10 @@ static int get_wave_state(struct mqd_manager *mm, void *mqd,
        if (copy_to_user(ctl_stack, &header, sizeof(header.wave_state)))
                return -EFAULT;
 
-       if (copy_to_user(ctl_stack + m->cp_hqd_cntl_stack_offset,
-                               mqd_ctl_stack + m->cp_hqd_cntl_stack_offset,
-                               *ctl_stack_used_size))
+       *ctl_stack_used_size = cntl_stack_size - cntl_stack_offset;
+
+       if (copy_to_user(ctl_stack + cntl_stack_offset, mqd_ctl_stack + cntl_stack_offset,
+                                       *ctl_stack_used_size))
                return -EFAULT;
 
        return 0;