From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 64A1512DDB8; Tue, 23 Jan 2024 00:16:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705968982; cv=none; b=QF82b9wSU/sRJU5ThkNVlfBCUtOQMUvz1TAOUcHV8wYiinRRWE+HpZCXmQpJM1/3EFBC2QwB68bsDxdQghNcR4kTGOkq7o4GY2qK/Dabm7pu3DRnvjiFkNRvf/E6PHnmjCkKkK93FYRkkTZ6QKxX0poJSmAsaknEaDVPVl4njBA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705968982; c=relaxed/simple; bh=z1MzaqgzMuWR+TRJc7Kfzf1aAc2AHvRPgJxd6jfeGug=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WR3ObV2XtdtrgBRTN6BNNerTBJXsHkuTuvDiEFRblMTIr7tY4ePxVSnigje09Gft/xPmOi6QN7cViq4I17EE/spJxgIr9q4OqD+5BKVfYFodKOFA6Rk1qD/MQAfLE4jujINEbptV7lqXIeuVVGS9NKNnVhnQBDJQmY3ENeeJ/Rs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=uWJyQNFf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="uWJyQNFf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2EF7CC433F1; Tue, 23 Jan 2024 00:16:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1705968982; bh=z1MzaqgzMuWR+TRJc7Kfzf1aAc2AHvRPgJxd6jfeGug=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uWJyQNFfBFlfuylYRLiDzcwxddpjFpEqhtiEbgvlEbmoVZoLc/29xYfNLBMPvmysw 1+J9SYcKNH56p/9/gcjGns+LZij/Y/pGY161yj/0c+SWwv5LnXHn8VAbC48+/+ew6W T9fRS4JU7CwkAAfXfdrzW4dE8DtrWQRsenqLb2DA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Liam Howlett , Minchan Kim , Alice Ryhl , Carlos Llamas Subject: [PATCH 5.4 140/194] binder: fix use-after-free in shinkers callback Date: Mon, 22 Jan 2024 15:57:50 -0800 Message-ID: <20240122235725.239958227@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240122235719.206965081@linuxfoundation.org> References: <20240122235719.206965081@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Carlos Llamas commit 3f489c2067c5824528212b0fc18b28d51332d906 upstream. The mmap read lock is used during the shrinker's callback, which means that using alloc->vma pointer isn't safe as it can race with munmap(). As of commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") the mmap lock is downgraded after the vma has been isolated. I was able to reproduce this issue by manually adding some delays and triggering page reclaiming through the shrinker's debug sysfs. The following KASAN report confirms the UAF: ================================================================== BUG: KASAN: slab-use-after-free in zap_page_range_single+0x470/0x4b8 Read of size 8 at addr ffff356ed50e50f0 by task bash/478 CPU: 1 PID: 478 Comm: bash Not tainted 6.6.0-rc5-00055-g1c8b86a3799f-dirty #70 Hardware name: linux,dummy-virt (DT) Call trace: zap_page_range_single+0x470/0x4b8 binder_alloc_free_page+0x608/0xadc __list_lru_walk_one+0x130/0x3b0 list_lru_walk_node+0xc4/0x22c binder_shrink_scan+0x108/0x1dc shrinker_debugfs_scan_write+0x2b4/0x500 full_proxy_write+0xd4/0x140 vfs_write+0x1ac/0x758 ksys_write+0xf0/0x1dc __arm64_sys_write+0x6c/0x9c Allocated by task 492: kmem_cache_alloc+0x130/0x368 vm_area_alloc+0x2c/0x190 mmap_region+0x258/0x18bc do_mmap+0x694/0xa60 vm_mmap_pgoff+0x170/0x29c ksys_mmap_pgoff+0x290/0x3a0 __arm64_sys_mmap+0xcc/0x144 Freed by task 491: kmem_cache_free+0x17c/0x3c8 vm_area_free_rcu_cb+0x74/0x98 rcu_core+0xa38/0x26d4 rcu_core_si+0x10/0x1c __do_softirq+0x2fc/0xd24 Last potentially related work creation: __call_rcu_common.constprop.0+0x6c/0xba0 call_rcu+0x10/0x1c vm_area_free+0x18/0x24 remove_vma+0xe4/0x118 do_vmi_align_munmap.isra.0+0x718/0xb5c do_vmi_munmap+0xdc/0x1fc __vm_munmap+0x10c/0x278 __arm64_sys_munmap+0x58/0x7c Fix this issue by performing instead a vma_lookup() which will fail to find the vma that was isolated before the mmap lock downgrade. Note that this option has better performance than upgrading to a mmap write lock which would increase contention. Plus, mmap_write_trylock() has been recently removed anyway. Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") Cc: stable@vger.kernel.org Cc: Liam Howlett Cc: Minchan Kim Reviewed-by: Alice Ryhl Signed-off-by: Carlos Llamas Link: https://lore.kernel.org/r/20231201172212.1813387-3-cmllamas@google.com [cmllamas: use find_vma() instead of vma_lookup() as commit ce6d42f2e4a2 is missing in v5.4. This only works because we check the vma against our cached alloc->vma pointer. Also, unlock via up_read() instead of mmap_read_unlock() as commit d8ed45c5dcd4 is also missing in v5.4.] Signed-off-by: Carlos Llamas Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder_alloc.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -954,7 +954,9 @@ enum lru_status binder_alloc_free_page(s goto err_mmget; if (!down_read_trylock(&mm->mmap_sem)) goto err_down_read_mmap_sem_failed; - vma = binder_alloc_get_vma(alloc); + vma = find_vma(mm, page_addr); + if (vma && vma != binder_alloc_get_vma(alloc)) + goto err_invalid_vma; list_lru_isolate(lru, item); spin_unlock(lock); @@ -980,6 +982,8 @@ enum lru_status binder_alloc_free_page(s mutex_unlock(&alloc->mutex); return LRU_REMOVED_RETRY; +err_invalid_vma: + up_read(&mm->mmap_sem); err_down_read_mmap_sem_failed: mmput_async(mm); err_mmget: