Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755407Ab1BIOMy (ORCPT ); Wed, 9 Feb 2011 09:12:54 -0500 Received: from mx1.vsecurity.com ([209.67.252.12]:60196 "EHLO mx1.vsecurity.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755260Ab1BIOMx (ORCPT ); Wed, 9 Feb 2011 09:12:53 -0500 Subject: [PATCH] btrfs: prevent heap corruption in btrfs_ioctl_space_info() From: Dan Rosenberg To: chris.mason@oracle.com Cc: security@kernel.org, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, stable@kernel.org Content-Type: text/plain; charset="UTF-8" Date: Wed, 09 Feb 2011 09:12:46 -0500 Message-ID: <1297260766.2327.40.camel@dan> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2465 Lines: 66 Commit bf5fc093c5b625e4259203f1cee7ca73488a5620 refactored btrfs_ioctl_space_info() and introduced several security issues. space_args.space_slots is an unsigned 64-bit type controlled by a possibly unprivileged caller. The comparison as a signed int type allows providing values that are treated as negative and cause the subsequent allocation size calculation to wrap, or be truncated to 0. By providing a size that's truncated to 0, kmalloc() will return ZERO_SIZE_PTR. It's also possible to provide a value smaller than the slot count. The subsequent loop ignores the allocation size when copying data in, resulting in a heap overflow or write to ZERO_SIZE_PTR. The fix changes the slot count type and comparison typecast to u64, which prevents truncation or signedness errors, and also ensures that we don't copy more data than we've allocated in the subsequent loop. Note that zero-size allocations are no longer possible since there is already an explicit check for space_args.space_slots being 0 and truncation of this value is no longer an issue. Signed-off-by: Dan Rosenberg --- fs/btrfs/ioctl.c | 10 ++++++++-- 1 files changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 02d224e..f1a43df 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2208,7 +2208,7 @@ long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg) int num_types = 4; int alloc_size; int ret = 0; - int slot_count = 0; + u64 slot_count = 0; int i, c; if (copy_from_user(&space_args, @@ -2247,7 +2247,7 @@ long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg) goto out; } - slot_count = min_t(int, space_args.space_slots, slot_count); + slot_count = min_t(u64, space_args.space_slots, slot_count); alloc_size = sizeof(*dest) * slot_count; @@ -2267,6 +2267,12 @@ long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg) for (i = 0; i < num_types; i++) { struct btrfs_space_info *tmp; + /* Don't copy in more than we allocated */ + if (!slot_count) + break; + + slot_count--; + info = NULL; rcu_read_lock(); list_for_each_entry_rcu(tmp, &root->fs_info->space_info, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/