From 547da76b5777859f98bb78e6b57f19463f803c04 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 26 Oct 2017 14:00:32 +0100 Subject: [PATCH] drm/i915: Hold rcu_read_lock when iterating over the radixtree (vma idr) Kasan spotted [IGT] gem_tiled_pread_pwrite: exiting, ret=0 ================================================================== BUG: KASAN: use-after-free in __i915_gem_object_reset_page_iter+0x15c/0x170 [i915] Read of size 8 at addr ffff8801359da310 by task kworker/3:2/182 CPU: 3 PID: 182 Comm: kworker/3:2 Tainted: G U 4.14.0-rc6-CI-Custom_3340+ #1 Hardware name: Intel Corp. Geminilake/GLK RVP1 DDR4 (05), BIOS GELKRVPA.X64.0062.B30.1708222146 08/22/2017 Workqueue: events __i915_gem_free_work [i915] Call Trace: dump_stack+0x68/0xa0 print_address_description+0x78/0x290 ? __i915_gem_object_reset_page_iter+0x15c/0x170 [i915] kasan_report+0x23d/0x350 __asan_report_load8_noabort+0x19/0x20 __i915_gem_object_reset_page_iter+0x15c/0x170 [i915] ? i915_gem_object_truncate+0x100/0x100 [i915] ? lock_acquire+0x380/0x380 __i915_gem_object_put_pages+0x30d/0x530 [i915] __i915_gem_free_objects+0x551/0xbd0 [i915] ? lock_acquire+0x13e/0x380 __i915_gem_free_work+0x4e/0x70 [i915] process_one_work+0x6f6/0x1590 ? pwq_dec_nr_in_flight+0x2b0/0x2b0 worker_thread+0xe6/0xe90 ? pci_mmcfg_check_reserved+0x110/0x110 kthread+0x309/0x410 ? process_one_work+0x1590/0x1590 ? kthread_create_on_node+0xb0/0xb0 ret_from_fork+0x27/0x40 Allocated by task 1801: save_stack_trace+0x1b/0x20 kasan_kmalloc+0xee/0x190 kasan_slab_alloc+0x12/0x20 kmem_cache_alloc+0xdc/0x2e0 radix_tree_node_alloc.constprop.12+0x48/0x330 __radix_tree_create+0x274/0x480 __radix_tree_insert+0xa2/0x610 i915_gem_object_get_sg+0x224/0x670 [i915] i915_gem_object_get_page+0xb5/0x1c0 [i915] i915_gem_pread_ioctl+0x822/0xf60 [i915] drm_ioctl_kernel+0x13f/0x1c0 drm_ioctl+0x6cf/0x980 do_vfs_ioctl+0x184/0xf30 SyS_ioctl+0x41/0x70 entry_SYSCALL_64_fastpath+0x1c/0xb1 Freed by task 37: save_stack_trace+0x1b/0x20 kasan_slab_free+0xaf/0x190 kmem_cache_free+0xbf/0x340 radix_tree_node_rcu_free+0x79/0x90 rcu_process_callbacks+0x46d/0xf40 __do_softirq+0x21c/0x8d3 The buggy address belongs to the object at ffff8801359da0f0 which belongs to the cache radix_tree_node of size 576 The buggy address is located 544 bytes inside of 576-byte region [ffff8801359da0f0, ffff8801359da330) The buggy address belongs to the page: page:ffffea0004d67600 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 flags: 0x8000000000008100(slab|head) raw: 8000000000008100 0000000000000000 0000000000000000 0000000100110011 raw: ffffea0004b52920 ffffea0004b38020 ffff88015b416a80 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801359da200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801359da280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8801359da300: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc ^ ffff8801359da380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8801359da400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== Disabling lock debugging due to kernel taint which looks like the slab containing the radixtree iter was freed as we traversed the tree, taking the rcu read lock across the loop should prevent that (deferring all the frees until the end). Reported-by: Tomi Sarvela Fixes: d1b48c1e7184 ("drm/i915: Replace execbuf vma ht with an idr") Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Joonas Lahtinen Link: https://patchwork.freedesktop.org/patch/msgid/20171026130032.10677-2-chris@chris-wilson.co.uk Reviewed-by: Matthew Auld --- drivers/gpu/drm/i915/i915_gem_context.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c index 4f26f80b1b3e..10affb35ac56 100644 --- a/drivers/gpu/drm/i915/i915_gem_context.c +++ b/drivers/gpu/drm/i915/i915_gem_context.c @@ -104,6 +104,7 @@ static void lut_close(struct i915_gem_context *ctx) kmem_cache_free(ctx->i915->luts, lut); } + rcu_read_lock(); radix_tree_for_each_slot(slot, &ctx->handles_vma, &iter, 0) { struct i915_vma *vma = rcu_dereference_raw(*slot); struct drm_i915_gem_object *obj = vma->obj; @@ -115,6 +116,7 @@ static void lut_close(struct i915_gem_context *ctx) __i915_gem_object_release_unless_active(obj); } + rcu_read_unlock(); } static void i915_gem_context_free(struct i915_gem_context *ctx)