[PATCH v2 4/4] ext4: prevent getting empty inode buffer
From: Zhang Yi <yi.zhang@huawei.com>
Date: 2021-08-19 06:46:40
Subsystem:
ext4 file system, filesystems (vfs and infrastructure), the rest · Maintainers:
"Theodore Ts'o", Alexander Viro, Christian Brauner, Linus Torvalds
In ext4_get_inode_loc(), we may skip IO and get an zero && uptodate inode buffer when the inode monopolize an inode block for performance reason. For most cases, ext4_mark_iloc_dirty() will fill the inode buffer to make it fine, but we could miss this call if something bad happened. Finally, __ext4_get_inode_loc_noinmem() may probably get an empty inode buffer and trigger ext4 error. For example, if we remove a nonexistent xattr on inode A, ext4_xattr_set_handle() will return ENODATA before invoking ext4_mark_iloc_dirty(), it will left an uptodate but zero buffer. We will get checksum error message in ext4_iget() when getting inode again. EXT4-fs error (device sda): ext4_lookup:1784: inode #131074: comm cat: iget: checksum invalid Even worse, if we allocate another inode B at the same inode block, it will corrupt the inode A on disk when write back inode B. So this patch postpone the init and mark buffer uptodate logic until before filling correct inode data in ext4_do_update_inode() if skip read I/O, ensure the buffer is real uptodate. Signed-off-by: Zhang Yi <yi.zhang@huawei.com> --- fs/ext4/inode.c | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d0d7a5295bf9..02d910c9d8f1 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c@@ -4367,9 +4367,11 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino, } brelse(bitmap_bh); if (i == start + inodes_per_block) { - /* all other inodes are free, so skip I/O */ - memset(bh->b_data, 0, bh->b_size); - set_buffer_uptodate(bh); + /* + * All other inodes are free, skip I/O. Return + * un-inited buffer (which is postponed until + * before filling inode data) immediately. + */ unlock_buffer(bh); goto has_buffer; }
@@ -5026,6 +5028,24 @@ static int ext4_do_update_inode(handle_t *handle, gid_t i_gid; projid_t i_projid; + /* + * If the buffer is not uptodate, it means all information of inode + * in memory and we got this buffer without reading the block. We + * must be cautious that once we mark the buffer as uptodate, we + * rely on filling in the correct inode data later in this function. + * Otherwise if we getting the left falsepositive buffer when + * creating other inode on the same block, it could corrupt the + * inode data on disk. + */ + if (!buffer_uptodate(bh)) { + lock_buffer(bh); + if (!buffer_uptodate(bh)) { + memset(bh->b_data, 0, bh->b_size); + set_buffer_uptodate(bh); + } + unlock_buffer(bh); + } + spin_lock(&ei->i_raw_lock); /* For fields not tracked in the in-memory inode,
--
2.31.1