| Message ID | 20230816052104.3374-1-g.ottinger@gmx.at |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [v2] ext2: fix datatype of block number in ext2_xattr_set2() | expand |
On Wed 16-08-23 07:31:34, Georg Ottinger wrote: > I missed the proper format string for the debug message. Thanks. I've fixed up the patch in my tree. > answering Andreas question - I did check the remaining calls to > ext2_new_block(), ext2_new_blocks() and ext2_free_blocks() within the > ext2 directory - here the block argument is either unsigned long or > ext2_fsblk_t (which is a typedef to unsigend long) - However I want to > mention that the use of unsigned long / ext2_fsblk_t is inconsistent. I > guess that ext2_fsblk_t should be the prefered data type. Yes, that's correct. We should be using ext2_fsblk_t all over the place. In fact unsigned long is also a questionable type. On disk the block number is u32, so unsigned long is pointlessly big on 64-bit archs and just using u32 as ext2_fsblk_t would make more sense. But then it's possible there are some overflows in the code currently hidden by the fact that most of the testing happens on 64-bit where long is 64-bit. So the switch would need somewhat careful review. Honza
diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c index 8906ba479..89517937d 100644 --- a/fs/ext2/xattr.c +++ b/fs/ext2/xattr.c @@ -742,10 +742,10 @@ ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh, /* We need to allocate a new block */ ext2_fsblk_t goal = ext2_group_first_block_no(sb, EXT2_I(inode)->i_block_group); - int block = ext2_new_block(inode, goal, &error); + ext2_fsblk_t block = ext2_new_block(inode, goal, &error); if (error) goto cleanup; - ea_idebug(inode, "creating block %d", block); + ea_idebug(inode, "creating block %lu", block); new_bh = sb_getblk(sb, block); if (unlikely(!new_bh)) {
I run a small server that uses external hard drives for backups. The backup software I use uses ext2 filesystems with 4KiB block size and the server is running SELinux and therefore relies on xattr. I recently upgraded the hard drives from 4TB to 12TB models. I noticed that after transferring some TBs I got a filesystem error "Freeing blocks not in datazone - block = 18446744071529317386, count = 1" and the backup process stopped. Trying to fix the fs with e2fsck resulted in a completely corrupted fs. The error probably came from ext2_free_blocks(), and because of the large number 18e19 this problem immediately looked like some kind of integer overflow. Whereas the 4TB fs was about 1e9 blocks, the new 12TB is about 3e9 blocks. So, searching the ext2 code, I came across the line in fs/ext2/xattr.c:745 where ext2_new_block() is called and the resulting block number is stored in the variable block as an int datatype. If a block with a block number greater than INT32_MAX is returned, this variable overflows and the call to sb_getblk() at line fs/ext2/xattr.c:750 fails, then the call to ext2_free_blocks() produces the error. Signed-off-by: Georg Ottinger <g.ottinger@gmx.at> --- fs/ext2/xattr.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) -- 2.17.1