From ff0031d848a0cd7002606f9feef958de8d5edf19 Mon Sep 17 00:00:00 2001 From: Carlos Maiolino Date: Tue, 5 Jul 2016 22:02:41 -0400 Subject: ext2: fix filesystem deadlock while reading corrupted xattr block This bug can be reproducible with fsfuzzer, although, I couldn't reproduce it 100% of my tries, it is quite easily reproducible. During the deletion of an inode, ext2_xattr_delete_inode() does not check if the block pointed by EXT2_I(inode)->i_file_acl is a valid data block, this might lead to a deadlock, when i_file_acl == 1, and the filesystem block size is 1024. In that situation, ext2_xattr_delete_inode, will load the superblock's buffer head (instead of a valid i_file_acl block), and then lock that buffer head, which, ext2_sync_super will also try to lock, making the filesystem deadlock in the following stack trace: root 17180 0.0 0.0 113660 660 pts/0 D+ 07:08 0:00 rmdir /media/test/dir1 [] __sync_dirty_buffer+0xaf/0x100 [] sync_dirty_buffer+0x13/0x20 [] ext2_sync_super+0xb7/0xc0 [ext2] [] ext2_error+0x119/0x130 [ext2] [] ext2_free_blocks+0x83/0x350 [ext2] [] ext2_xattr_delete_inode+0x173/0x190 [ext2] [] ext2_evict_inode+0xc9/0x130 [ext2] [] evict+0xb3/0x180 [] iput+0x1b8/0x240 [] d_delete+0x11c/0x150 [] vfs_rmdir+0xfe/0x120 [] do_rmdir+0x17e/0x1f0 [] SyS_rmdir+0x16/0x20 [] entry_SYSCALL_64_fastpath+0x1a/0xa4 [] 0xffffffffffffffff Fix this by using the same approach ext4 uses to test data blocks validity, implementing ext2_data_block_valid. An another possibility when the superblock is very corrupted, is that i_file_acl is 1, block_count is 1 and first_data_block is 0. For such situations, we might have i_file_acl pointing to a 'valid' block, but still step over the superblock. The approach I used was to also test if the superblock is not in the range described by ext2_data_block_valid() arguments Signed-off-by: Carlos Maiolino Signed-off-by: Theodore Ts'o --- fs/ext2/xattr.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'fs/ext2/xattr.c') diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c index 1a5e3bff0b63..b7f896f3f7a7 100644 --- a/fs/ext2/xattr.c +++ b/fs/ext2/xattr.c @@ -759,10 +759,19 @@ void ext2_xattr_delete_inode(struct inode *inode) { struct buffer_head *bh = NULL; + struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb); down_write(&EXT2_I(inode)->xattr_sem); if (!EXT2_I(inode)->i_file_acl) goto cleanup; + + if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 0)) { + ext2_error(inode->i_sb, "ext2_xattr_delete_inode", + "inode %ld: xattr block %d is out of data blocks range", + inode->i_ino, EXT2_I(inode)->i_file_acl); + goto cleanup; + } + bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl); if (!bh) { ext2_error(inode->i_sb, "ext2_xattr_delete_inode", -- cgit v1.2.3