[ 097/108] UBI: fix a horrible memory deallocation bug

[Greg Kroah-Hartman]

From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>

3.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>

commit 78b495c39add820ab66ab897af9bd77a5f2e91f6 upstream.

UBI was mistakingly using 'kfree()' instead of 'kmem_cache_free()' when
freeing "attach eraseblock" structures in vtbl.c. Thankfully, this happened
only when we were doing auto-format, so many systems were unaffected. However,
there are still many users affected.

It is strange, but the system did not crash and nothing bad happened when
the SLUB memory allocator was used. However, in case of SLOB we observed an
crash right away.

This problem was introduced in 2.6.39 by commit
"6c1e875 UBI: add slab cache for ubi_scan_leb objects"

A note for stable trees:
  Because variable were renamed, this won't cleanly apply to older kernels.
  Changing names like this should help:
	1. ai -> si
	2. aeb_slab_cache -> seb_slab_cache
	3. new_aeb -> new_seb

Reported-by: Richard Genoud <richard.genoud@xxxxxxxxx>
Tested-by: Richard Genoud <richard.genoud@xxxxxxxxx>
Tested-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/mtd/ubi/vtbl.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/mtd/ubi/vtbl.c
+++ b/drivers/mtd/ubi/vtbl.c
@@ -340,7 +340,7 @@ retry:
 	 * of this LEB as it will be deleted and freed in 'ubi_add_to_av()'.
 	 */
 	err = ubi_add_to_av(ubi, ai, new_aeb->pnum, new_aeb->ec, vid_hdr, 0);
-	kfree(new_aeb);
+	kmem_cache_free(ai->aeb_slab_cache, new_aeb);
 	ubi_free_vid_hdr(ubi, vid_hdr);
 	return err;
 
@@ -353,7 +353,7 @@ write_error:
 		list_add(&new_aeb->u.list, &ai->erase);
 		goto retry;
 	}
-	kfree(new_aeb);
+	kmem_cache_free(ai->aeb_slab_cache, new_aeb);
 out_free:
 	ubi_free_vid_hdr(ubi, vid_hdr);
 	return err;


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