mm: kmemleak: avoid deadlock on the kmemleak object insertion error path
authorCatalin Marinas <catalin.marinas@arm.com>
Wed, 24 Jun 2015 23:58:34 +0000 (16:58 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 25 Jun 2015 00:49:45 +0000 (17:49 -0700)
commit9d5a4c730dd164f6f1b4ed6690fbe2667e5149ea
tree6fc2ada2616ddbf4f41d849217bea934509c5684
parent5f369f374ba4889fe3c17883402db5ee8d254216
mm: kmemleak: avoid deadlock on the kmemleak object insertion error path

While very unlikely (usually kmemleak or sl*b bug), the create_object()
function in mm/kmemleak.c may fail to insert a newly allocated object into
the rb tree.  When this happens, kmemleak disables itself and prints
additional information about the object already found in the rb tree.
Such printing is done with the parent->lock acquired, however the
kmemleak_lock is already held.  This is a potential race with the scanning
thread which acquires object->lock and kmemleak_lock in a

This patch removes the locking around the 'parent' object information
printing.  Such object cannot be freed or removed from object_tree_root
and object_list since kmemleak_lock is already held.  There is a very
small risk that some of the object data is being modified on another CPU
but the only downside is inconsistent information printing.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/kmemleak.c