From 7591c127f3b17d5879f18819cad7058bf3a2e276 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 4 Nov 2024 11:19:44 +0000 Subject: kmemleak: iommu/iova: fix transient kmemleak false positive The introduction of iova_depot_pop() in 911aa1245da8 ("iommu/iova: Make the rcache depot scale better") confused kmemleak by moving a struct iova_magazine object from a singly linked list to rcache->depot and resetting the 'next' pointer referencing it. Unlike doubly linked lists, the content of the object being referred is never changed on removal from a singly linked list and the kmemleak checksum heuristics do not detect such scenario. This leads to false positives like: unreferenced object 0xffff8881a5301000 (size 1024): comm "softirq", pid 0, jiffies 4306297099 (age 462.991s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 e7 7d 05 00 00 00 00 00 .........}...... 0f b4 05 00 00 00 00 00 b4 96 05 00 00 00 00 00 ................ backtrace: [] __kmem_cache_alloc_node+0x1e8/0x320 [] kmalloc_trace+0x2a/0x60 [] free_iova_fast+0x28e/0x4e0 [] fq_ring_free_locked+0x1b0/0x310 [] fq_flush_timeout+0x19d/0x2e0 [] call_timer_fn+0x19a/0x5c0 [] __run_timers+0x78b/0xb80 [] run_timer_softirq+0x5d/0xd0 [] __do_softirq+0x205/0x8b5 Introduce kmemleak_transient_leak() which resets the object checksum requiring another scan pass before it is reported (if still unreferenced). Call this new API in iova_depot_pop(). Link: https://lkml.kernel.org/r/20241104111944.2207155-1-catalin.marinas@arm.com Link: https://lore.kernel.org/r/ZY1osaGLyT-sdKE8@shredder/ Signed-off-by: Catalin Marinas Reported-by: Ido Schimmel Tested-by: Ido Schimmel Acked-by: Robin Murphy Cc: Joerg Roedel Cc: Will Deacon Signed-off-by: Andrew Morton --- Documentation/dev-tools/kmemleak.rst | 1 + 1 file changed, 1 insertion(+) (limited to 'Documentation/dev-tools') diff --git a/Documentation/dev-tools/kmemleak.rst b/Documentation/dev-tools/kmemleak.rst index 2cb00b53339f..7d784e03f3f9 100644 --- a/Documentation/dev-tools/kmemleak.rst +++ b/Documentation/dev-tools/kmemleak.rst @@ -161,6 +161,7 @@ See the include/linux/kmemleak.h header for the functions prototype. - ``kmemleak_free_percpu`` - notify of a percpu memory block freeing - ``kmemleak_update_trace`` - update object allocation stack trace - ``kmemleak_not_leak`` - mark an object as not a leak +- ``kmemleak_transient_leak`` - mark an object as a transient leak - ``kmemleak_ignore`` - do not scan or report an object as leak - ``kmemleak_scan_area`` - add scan areas inside a memory block - ``kmemleak_no_scan`` - do not scan a memory block -- cgit v1.3.1