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 77F13241FC; Thu, 18 Jan 2024 11:02:33 +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=1705575753; cv=none; b=p0ddzRIo1q8VU3w5bk0SqDFZ12gjX0aaDdssyLeYrnbL75+bs3+vjtLYNT3LWWe+dYcDAL9+B1CMCwRvrD/cZEMLoZVYq1k1fQ9vjjnt5F24MLs/SfjSqpO2AAkKvz4zEqXmbxMiYrmyXy6q60vMuMVxvB3BuLNqdrdKUk97rJs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705575753; c=relaxed/simple; bh=9cADCsr0LrknVhlsWuSE4RPEVdHIP/4rH5zzXxmSqFo=; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID: X-Mailer:In-Reply-To:References:User-Agent:X-stable: X-Patchwork-Hint:MIME-Version:Content-Transfer-Encoding; b=pBLOppH7bedmX/GhXBBK8MYzJ27h8B5rlD6tdrCafyDRCzI7b4DbPtHSjcLo5waX4+m5PYpNnzEzSxeP7U+R6y1AaUSkt50LBUdKZpNxe+RBv9TP7KFeLFInlt1UzaO7JM932sadrVGAM3Kf2oT+LdDMGoOjm0k7jQZn8BYCl0A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=AYU5YN1O; 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="AYU5YN1O" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BDA31C433C7; Thu, 18 Jan 2024 11:02:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1705575753; bh=9cADCsr0LrknVhlsWuSE4RPEVdHIP/4rH5zzXxmSqFo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AYU5YN1ORPlq45m46BJPEKqHamzgHzYs2Qu+rley3Jby80WKADnBhwzaAr64t2vta w5WOD3CCmuLkJjWHPNJYJJpBS0ZSHLyYWhnK8Cb+qAGuK4M10JjKETv+Tyt8ZSQ9o7 5OgylgnS+UL0S7vhwFpT5l9Ks5H9ISBzxN3EjofI= 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 6.1 091/100] binder: fix use-after-free in shinkers callback Date: Thu, 18 Jan 2024 11:49:39 +0100 Message-ID: <20240118104314.866432411@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240118104310.892180084@linuxfoundation.org> References: <20240118104310.892180084@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 6.1-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 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 @@ -1005,7 +1005,9 @@ enum lru_status binder_alloc_free_page(s goto err_mmget; if (!mmap_read_trylock(mm)) goto err_mmap_read_lock_failed; - vma = binder_alloc_get_vma(alloc); + vma = vma_lookup(mm, page_addr); + if (vma && vma != binder_alloc_get_vma(alloc)) + goto err_invalid_vma; list_lru_isolate(lru, item); spin_unlock(lock); @@ -1031,6 +1033,8 @@ enum lru_status binder_alloc_free_page(s mutex_unlock(&alloc->mutex); return LRU_REMOVED_RETRY; +err_invalid_vma: + mmap_read_unlock(mm); err_mmap_read_lock_failed: mmput_async(mm); err_mmget: