ubifs: error unwinding trouble

[Adrian Hunter]

Daniel Mack wrote:
> On a recent git kernel, the error unwinding for UBIFS seems to have some
> problem, most probably a double-free or something similar.
> 
> When UBI is pointed to the right mtd partition (using command line
> arguments) , everything is fine. But when it's (accidentionally) set to
> some very small mtd, the attach process fails. Which wouldn't be a bad
> thing by itself, but it somehow messes up the slub/slab allocators then
> which causes very strange memory corruption effects - see the backtrace
> below.
> 
> The Ooops itself is unreleated to UBI, but it does not occur when UBI
> succeeds in attaching the volume.
> 
> Any idea? I searched for awhile but couldn't see anything obvious.

Looks like a double free of the eba_tbl

This might help:

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index 0f2034c..e4d9ef0 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -1254,6 +1254,7 @@ out_free:
                if (!ubi->volumes[i])
                        continue;
                kfree(ubi->volumes[i]->eba_tbl);
+               ubi->volumes[i]->eba_tbl = NULL;
        }
        return err;
 }