From 0eaf33265f8a2e0d76ee6db1ad74ee4422efb122 Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <slyfox@gentoo.org>
Date: Sun, 10 Apr 2011 23:19:53 +0300
Subject: [PATCH] btrfs: properly handle overlapping areas in memmove_extent_buffer
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Fix data corruption caused by memcpy() usage on overlapping data.
I've observed it first when found out usermode linux crash on btrfs.
?all chain is the following:
------------[ cut here ]------------
WARNING: at /home/slyfox/linux-2.6/fs/btrfs/extent_io.c:3900 memcpy_extent_buffer+0x1a5/0x219()
Call Trace:
6fa39a58: [<601b495e>] _raw_spin_unlock_irqrestore+0x18/0x1c
6fa39a68: [<60029ad9>] warn_slowpath_common+0x59/0x70
6fa39aa8: [<60029b05>] warn_slowpath_null+0x15/0x17
6fa39ab8: [<600efc97>] memcpy_extent_buffer+0x1a5/0x219
6fa39b48: [<600efd9f>] memmove_extent_buffer+0x94/0x208
6fa39bc8: [<600becbf>] btrfs_del_items+0x214/0x473
6fa39c78: [<600ce1b0>] btrfs_delete_one_dir_name+0x7c/0xda
6fa39cc8: [<600dad6b>] __btrfs_unlink_inode+0xad/0x25d
6fa39d08: [<600d7864>] btrfs_start_transaction+0xe/0x10
6fa39d48: [<600dc9ff>] btrfs_unlink_inode+0x1b/0x3b
6fa39d78: [<600e04bc>] btrfs_unlink+0x70/0xef
6fa39dc8: [<6007f0d0>] vfs_unlink+0x58/0xa3
6fa39df8: [<60080278>] do_unlinkat+0xd4/0x162
6fa39e48: [<600517db>] call_rcu_sched+0xe/0x10
6fa39e58: [<600452a8>] __put_cred+0x58/0x5a
6fa39e78: [<6007446c>] sys_faccessat+0x154/0x166
6fa39ed8: [<60080317>] sys_unlink+0x11/0x13
6fa39ee8: [<60016b80>] handle_syscall+0x58/0x70
6fa39f08: [<60021377>] userspace+0x2d4/0x381
6fa39fc8: [<60014507>] fork_handler+0x62/0x69
---[ end trace 70b0ca2ef0266b93 ]---
http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg09302.html
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
---
fs/btrfs/extent_io.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
@@ -3897,6 +3897,7 @@ static void copy_pages(struct page *dst_page, struct page *src_page,
else
src_kaddr = dst_kaddr;
+ BUG_ON(abs(src_off - dst_off) < len);
memcpy(dst_kaddr + dst_off, src_kaddr + src_off, len);
kunmap_atomic(dst_kaddr, KM_USER0);
if (dst_page != src_page)
@@ -3970,7 +3971,7 @@ void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
"len %lu len %lu\n", dst_offset, len, dst->len);
BUG_ON(1);
}
- if (dst_offset < src_offset) {
+ if (abs(dst_offset - src_offset) >= len) {
memcpy_extent_buffer(dst, dst_offset, src_offset, len);
return;
}
--
1.7.3.4