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authorCarlos Maiolino <cmaiolino@redhat.com>2016-07-05 22:02:41 -0400
committerTheodore Ts'o <tytso@mit.edu>2016-07-05 22:02:41 -0400
commitff0031d848a0cd7002606f9feef958de8d5edf19 (patch)
treebbc3819f57ac54666716b1c6c5dc21085612edc7 /fs/ext2/balloc.c
parent079788d01e7ba9d7366d7bd2a0db9cab5944e85b (diff)
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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 [<ffffffff8125da9f>] __sync_dirty_buffer+0xaf/0x100 [<ffffffff8125db03>] sync_dirty_buffer+0x13/0x20 [<ffffffffa03f0d57>] ext2_sync_super+0xb7/0xc0 [ext2] [<ffffffffa03f10b9>] ext2_error+0x119/0x130 [ext2] [<ffffffffa03e9d93>] ext2_free_blocks+0x83/0x350 [ext2] [<ffffffffa03f3d03>] ext2_xattr_delete_inode+0x173/0x190 [ext2] [<ffffffffa03ee9e9>] ext2_evict_inode+0xc9/0x130 [ext2] [<ffffffff8123fd23>] evict+0xb3/0x180 [<ffffffff81240008>] iput+0x1b8/0x240 [<ffffffff8123c4ac>] d_delete+0x11c/0x150 [<ffffffff8122fa7e>] vfs_rmdir+0xfe/0x120 [<ffffffff812340ee>] do_rmdir+0x17e/0x1f0 [<ffffffff81234dd6>] SyS_rmdir+0x16/0x20 [<ffffffff81838cf2>] entry_SYSCALL_64_fastpath+0x1a/0xa4 [<ffffffffffffffff>] 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 <cmaiolino@redhat.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext2/balloc.c')
-rw-r--r--fs/ext2/balloc.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
index 9f9992b37924..4c40c0786e16 100644
--- a/fs/ext2/balloc.c
+++ b/fs/ext2/balloc.c
@@ -1194,6 +1194,27 @@ static int ext2_has_free_blocks(struct ext2_sb_info *sbi)
}
/*
+ * Returns 1 if the passed-in block region is valid; 0 if some part overlaps
+ * with filesystem metadata blocksi.
+ */
+int ext2_data_block_valid(struct ext2_sb_info *sbi, ext2_fsblk_t start_blk,
+ unsigned int count)
+{
+ if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
+ (start_blk + count < start_blk) ||
+ (start_blk > le32_to_cpu(sbi->s_es->s_blocks_count)))
+ return 0;
+
+ /* Ensure we do not step over superblock */
+ if ((start_blk <= sbi->s_sb_block) &&
+ (start_blk + count >= sbi->s_sb_block))
+ return 0;
+
+
+ return 1;
+}
+
+/*
* ext2_new_blocks() -- core block(s) allocation function
* @inode: file inode
* @goal: given target block(filesystem wide)