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@xxxxxxxxxx>
---
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
