drm/amd/amdgpu: Fix GPR read from debugfs (v2)

The offset into the array was specified in bytes but should
be in terms of 32-bit words.  Also prevent large reads that
would also cause a buffer overread.

v2:  Read from correct offset from internal storage buffer.

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
index 00942af..02bb1be 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
@@ -784,11 +784,11 @@ static ssize_t amdgpu_debugfs_gpr_read(struct file *f, char __user *buf,
        ssize_t result = 0;
        uint32_t offset, se, sh, cu, wave, simd, thread, bank, *data;
 
-       if (size & 3 || *pos & 3)
+       if (size > 4096 || size & 3 || *pos & 3)
                return -EINVAL;
 
        /* decode offset */
-       offset = *pos & GENMASK_ULL(11, 0);
+       offset = (*pos & GENMASK_ULL(11, 0)) >> 2;
        se = (*pos & GENMASK_ULL(19, 12)) >> 12;
        sh = (*pos & GENMASK_ULL(27, 20)) >> 20;
        cu = (*pos & GENMASK_ULL(35, 28)) >> 28;
@@ -826,7 +826,7 @@ static ssize_t amdgpu_debugfs_gpr_read(struct file *f, char __user *buf,
        while (size) {
                uint32_t value;
 
-               value = data[offset++];
+               value = data[result >> 2];
                r = put_user(value, (uint32_t *)buf);
                if (r) {
                        result = r;