hpfs: deadlock and race in directory lseek()
For one thing, there's an ABBA deadlock on hpfs fs-wide lock and i_mutex
in hpfs_dir_lseek() - there's a lot of methods that grab the former with
the caller already holding the latter, so it must take i_mutex first.
For another, locking the damn thing, carefully validating the offset,
then dropping locks and assigning the offset is obviously racy.
Moreover, we _must_ do hpfs_add_pos(), or the machinery in dnode.c
won't modify the sucker on B-tree surgeries.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/hpfs/dir.c b/fs/hpfs/dir.c
index 546f6d3..834ac13 100644
--- a/fs/hpfs/dir.c
+++ b/fs/hpfs/dir.c
@@ -33,25 +33,27 @@
if (whence == SEEK_DATA || whence == SEEK_HOLE)
return -EINVAL;
+ mutex_lock(&i->i_mutex);
hpfs_lock(s);
/*printk("dir lseek\n");*/
if (new_off == 0 || new_off == 1 || new_off == 11 || new_off == 12 || new_off == 13) goto ok;
- mutex_lock(&i->i_mutex);
pos = ((loff_t) hpfs_de_as_down_as_possible(s, hpfs_inode->i_dno) << 4) + 1;
while (pos != new_off) {
if (map_pos_dirent(i, &pos, &qbh)) hpfs_brelse4(&qbh);
else goto fail;
if (pos == 12) goto fail;
}
- mutex_unlock(&i->i_mutex);
+ hpfs_add_pos(i, &filp->f_pos);
ok:
+ filp->f_pos = new_off;
hpfs_unlock(s);
- return filp->f_pos = new_off;
-fail:
mutex_unlock(&i->i_mutex);
+ return new_off;
+fail:
/*printk("illegal lseek: %016llx\n", new_off);*/
hpfs_unlock(s);
+ mutex_unlock(&i->i_mutex);
return -ESPIPE;
}