[PATCH 5.10.y] drm/ttm: return an error when kmapping a BO without pages

[Sasha Levin <sashal@kernel.org>]

From: Jesse Zhang <Jesse.Zhang@amd.com>

[ Upstream commit fd485d47437ba1700dd47205a63b9f389a00aa36 ]

ttm_tt objects for imported sg tables (ttm_bo_type_sg, set up by
ttm_sg_tt_init() with TTM_TT_FLAG_EXTERNAL) only have DMA addresses and
no pages array. ttm_bo_kmap() and ttm_bo_vmap() still dereference
ttm->pages for them, so a driver that tries to CPU map such a BO oopses
instead of getting an error:

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  RIP: 0010:ttm_bo_kmap+0x26c/0x300 [ttm]
  Call Trace:
   amdgpu_bo_kmap+0x89/0xb0 [amdgpu]
   amdgpu_userq_fence_read_wptr+0x116/0x170 [amdgpu]
   amdgpu_userq_signal_ioctl+0x3fe/0xbb0 [amdgpu]

Return -EINVAL in that case, like ttm_bo_kmap_try_from_panic() already
checks for a missing pages array.

Fixes: 75a57669cbc8 ("drm/ttm: add ttm_sg_tt_init")
Cc: stable@vger.kernel.org
Suggested-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Link: https://patch.msgid.link/20261009103419.4122940-1-Jesse.Zhang@amd.com
[ sashal: adapted the check to the existing ttm_tt_populate() mapping path. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/ttm/ttm_bo_util.c | 4 ++++
 include/drm/ttm/ttm_bo_api.h      | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 1968df9743fcb..d234200e939bd 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -452,6 +452,10 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 	if (ret)
 		return ret;
 
+	/* Imported sg tables only come with DMA addresses, no pages to map. */
+	if (!ttm->pages)
+		return -EINVAL;
+
 	if (num_pages == 1 && (mem->placement & TTM_PL_FLAG_CACHED)) {
 		/*
 		 * We're mapping a single page, and the desired
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 09ccfee48fb45..ff46de1dcf0b4 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -523,7 +523,7 @@ static inline void *ttm_kmap_obj_virtual(struct ttm_bo_kmap_obj *map,
  *
  * Returns
  * -ENOMEM: Out of memory.
- * -EINVAL: Invalid range.
+ * -EINVAL: Invalid range or the BO has no pages to map.
  */
 int ttm_bo_kmap(struct ttm_buffer_object *bo, unsigned long start_page,
 		unsigned long num_pages, struct ttm_bo_kmap_obj *map);
-- 
2.53.0