drm/xe/reg_sr: Remove register pool

That pool implementation doesn't really work: if the krealloc happens to
move the memory and return another address, the entries in the xarray
become invalid, leading to use-after-free later:

	BUG: KASAN: slab-use-after-free in xe_reg_sr_apply_mmio+0x570/0x760 [xe]
	Read of size 4 at addr ffff8881244b2590 by task modprobe/2753

	Allocated by task 2753:
	 kasan_save_stack+0x39/0x70
	 kasan_save_track+0x14/0x40
	 kasan_save_alloc_info+0x37/0x60
	 __kasan_kmalloc+0xc3/0xd0
	 __kmalloc_node_track_caller_noprof+0x200/0x6d0
	 krealloc_noprof+0x229/0x380

Simplify the code to fix the bug. A better pooling strategy may be added
back later if needed.

Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241209232739.147417-2-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
(cherry picked from commit e5283bd4dfecbd3335f43b62a68e24dae23f59e4)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

diff --git a/drivers/gpu/drm/xe/xe_reg_sr.c b/drivers/gpu/drm/xe/xe_reg_sr.c
index e1a0e27cda14cac782b079a07bf8021246ecefa5..c13123008e9036e86c8f7d8557792cbd3009a0ad 100644 (file)
--- a/drivers/gpu/drm/xe/xe_reg_sr.c
+++ b/drivers/gpu/drm/xe/xe_reg_sr.c
@@ -27,46 +27,27 @@
 #include "xe_reg_whitelist.h"
 #include "xe_rtp_types.h"
 
-#define XE_REG_SR_GROW_STEP_DEFAULT    16
-
 static void reg_sr_fini(struct drm_device *drm, void *arg)
 {
        struct xe_reg_sr *sr = arg;
+       struct xe_reg_sr_entry *entry;
+       unsigned long reg;
+
+       xa_for_each(&sr->xa, reg, entry)
+               kfree(entry);
 
        xa_destroy(&sr->xa);
-       kfree(sr->pool.arr);
-       memset(&sr->pool, 0, sizeof(sr->pool));
 }
 
 int xe_reg_sr_init(struct xe_reg_sr *sr, const char *name, struct xe_device *xe)
 {
        xa_init(&sr->xa);
-       memset(&sr->pool, 0, sizeof(sr->pool));
-       sr->pool.grow_step = XE_REG_SR_GROW_STEP_DEFAULT;
        sr->name = name;
 
        return drmm_add_action_or_reset(&xe->drm, reg_sr_fini, sr);
 }
 EXPORT_SYMBOL_IF_KUNIT(xe_reg_sr_init);
 
-static struct xe_reg_sr_entry *alloc_entry(struct xe_reg_sr *sr)
-{
-       if (sr->pool.used == sr->pool.allocated) {
-               struct xe_reg_sr_entry *arr;
-
-               arr = krealloc_array(sr->pool.arr,
-                                    ALIGN(sr->pool.allocated + 1, sr->pool.grow_step),
-                                    sizeof(*arr), GFP_KERNEL);
-               if (!arr)
-                       return NULL;
-
-               sr->pool.arr = arr;
-               sr->pool.allocated += sr->pool.grow_step;
-       }
-
-       return &sr->pool.arr[sr->pool.used++];
-}
-
 static bool compatible_entries(const struct xe_reg_sr_entry *e1,
                               const struct xe_reg_sr_entry *e2)
 {
@@ -112,7 +93,7 @@ int xe_reg_sr_add(struct xe_reg_sr *sr,
                return 0;
        }
 
-       pentry = alloc_entry(sr);
+       pentry = kmalloc(sizeof(*pentry), GFP_KERNEL);
        if (!pentry) {
                ret = -ENOMEM;
                goto fail;

diff --git a/drivers/gpu/drm/xe/xe_reg_sr_types.h b/drivers/gpu/drm/xe/xe_reg_sr_types.h
index ad48a52b824a1846cb34819c7dd3a6b47124c78e..ebe11f237fa26dcc7122a123340b4e123b4086d6 100644 (file)
--- a/drivers/gpu/drm/xe/xe_reg_sr_types.h
+++ b/drivers/gpu/drm/xe/xe_reg_sr_types.h
@@ -20,12 +20,6 @@ struct xe_reg_sr_entry {
 };
 
 struct xe_reg_sr {
-       struct {
-               struct xe_reg_sr_entry *arr;
-               unsigned int used;
-               unsigned int allocated;
-               unsigned int grow_step;
-       } pool;
        struct xarray xa;
        const char *name;