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Tue, 14 Apr 2026 18:03:21 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=hdanton@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=hdanton@sina.com X-SMAIL-MID: 5193504456663 X-SMAIL-UIID: CE7A7A38408C490BBE28666CAA6EA88F-20260414-180321-1 From: Hillf Danton To: syzbot Cc: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [dri?] KASAN: slab-use-after-free Read in drm_gem_object_release_handle Date: Tue, 14 Apr 2026 18:03:12 +0800 Message-ID: <20260414100313.1832-1-hdanton@sina.com> In-Reply-To: <69dd24f4.a00a0220.468cb.004a.GAE@google.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > Date: Mon, 13 Apr 2026 10:16:36 -0700 [thread overview] > Hello, > > syzbot found the following issue on: > > HEAD commit: f5459048c38a Merge tag 'i2c-for-7.0-final' of git://git.ke.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1028d106580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=6754c86e8d9e4c91 > dashboard link: https://syzkaller.appspot.com/bug?extid=b2e951687503f32f74ce > compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1428d106580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17509036580000 #syz test --- x/drivers/gpu/drm/drm_gem.c +++ y/drivers/gpu/drm/drm_gem.c @@ -387,6 +387,26 @@ drm_gem_object_release_handle(int id, vo return 0; } +static int +drm_gem_object_release_idr_handle(int id, void *ptr, void *data) +{ + struct drm_file *filp = data; + struct drm_gem_object *obj, *tmp = ptr; + + spin_lock(&filp->table_lock); + obj = idr_find(&filp->object_idr, id); + if (obj != tmp) { + spin_unlock(&filp->table_lock); + return 0; + } + idr_remove(&filp->object_idr, id); + spin_unlock(&filp->table_lock); + if (IS_ERR_OR_NULL(obj)) + return 0; + drm_gem_object_release_handle(id, obj, filp); + return 0; +} + /** * drm_gem_handle_delete - deletes the given file-private handle * @filp: drm file-private structure to use for the handle look up @@ -404,7 +424,8 @@ drm_gem_handle_delete(struct drm_file *f spin_lock(&filp->table_lock); /* Check if we currently have a reference on the object */ - obj = idr_replace(&filp->object_idr, NULL, handle); + obj = idr_find(&filp->object_idr, handle); + idr_remove(&filp->object_idr, handle); spin_unlock(&filp->table_lock); if (IS_ERR_OR_NULL(obj)) return -EINVAL; @@ -412,11 +433,6 @@ drm_gem_handle_delete(struct drm_file *f /* Release driver's reference and decrement refcount. */ drm_gem_object_release_handle(handle, obj, filp); - /* And finally make the handle available for future allocations. */ - spin_lock(&filp->table_lock); - idr_remove(&filp->object_idr, handle); - spin_unlock(&filp->table_lock); - return 0; } EXPORT_SYMBOL(drm_gem_handle_delete); @@ -1086,7 +1102,7 @@ void drm_gem_release(struct drm_device *dev, struct drm_file *file_private) { idr_for_each(&file_private->object_idr, - &drm_gem_object_release_handle, file_private); + &drm_gem_object_release_idr_handle, file_private); idr_destroy(&file_private->object_idr); } --