idr: fix a critical misallocation bug, take#2
authorTejun Heo <tj@kernel.org>
Mon, 22 Feb 2010 20:44:19 +0000 (12:44 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 23 Feb 2010 03:50:34 +0000 (19:50 -0800)
commitd2e7276b6b5e4bc2148891a056d5862c5314342d
tree0013ab5f52d700dae771dcedf3f0f333486be5b6
parent701188374b6f1ef9cf7e4dce4a2e69ef4c0012ac
idr: fix a critical misallocation bug, take#2

This is retry of reverted 859ddf09743a8cc680af33f7259ccd0fd36bfe9d
("idr: fix a critical misallocation bug") which contained two bugs.

* pa[idp->layers] should be cleared even if it's not used by
  sub_alloc() because it's used by mark idr_mark_full().

* The original condition check also assigned pa[l] to p which the new
  code didn't do thus leaving p pointing at the wrong layer.

Both problems have been fixed and the idr code has received good amount
testing using userland testing setup where simple bitmap allocator is
run parallel to verify the result of idr allocation.

The bug this patch fixes is caused by sub_alloc() optimization path
bypassing out-of-room condition check and restarting allocation loop
with starting value higher than maximum allowed value.  For detailed
description, please read commit message of 859ddf09.

Signed-off-by: Tejun Heo <tj@kernel.org>
Based-on-patch-from: Eric Paris <eparis@redhat.com>
Reported-by: Eric Paris <eparis@redhat.com>
Tested-by: Stefan Lippers-Hollmann <s.l-h@gmx.de>
Tested-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/idr.c