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 initialization and mark buffer uptodate logic
until shortly before we fill correct inode data in ext4_do_update_inode()
if skip read I/O, ensure the buffer is really uptodate.
Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
---
fs/ext4/inode.c | 27 ++++++++++++++++++++++++---
1 file changed, 24 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 8323d3e8f393..000abb5696b0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4367,9 +4367,12 @@ 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
+ * uninitialized buffer immediately, initialization
+ * is postponed until shortly before we fill inode
+ * contents.
+ */
unlock_buffer(bh);
goto has_buffer;
}
@@ -5028,6 +5031,24 @@ 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 the
+ * inode is 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 left uptodate buffer without
+ * copying proper inode contents, we could corrupt the inode on
+ * disk after allocating another inode in the same block.
+ */
+ 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);
/*
--
2.31.1
