From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BFF9B4B0480; Fri, 7 Aug 2026 14:56:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786114569; cv=none; b=rYtkqJ/4F7VRxZwqffjTGvFoYWHI0ssvytBmWgAp/ODNjuh7CXX9Shy1GaC59kj4zpBp/CVwTr9YicTNPwDNtnmT2dgUkN2kI3jfYEmHq/XlkkdP5KBJ0WHsfHSr7hRWSfH70Nv1ZuJJA3ZzzjXZqk8yE9En9Hwre9yPSNXzDoc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786114569; c=relaxed/simple; bh=/VHmZjga0hHEaZN0b6uID81pCzx95MOXC9B3/aIiPLM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aBgZj8yE3+ZN2ZVqdpTKyWdy8Z6Slmf1RzYYoSRFRkLe4BdOiiUm2F7KuWxdvuI3cD+wzK8QZ1v1plDo2lhMtPsM+b59CIVk0mjJGYSTGTfduvEc2TKGj3OzvFWXw6VIFXRJ+dxwbwdz1i4YgmzdUjCNEqkskEVEyCe90pplhBs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zKUdbp4x; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="zKUdbp4x" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2E3DA1F000E9; Fri, 7 Aug 2026 14:56:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786114567; bh=v1QAOJ4wT17+qYQxCCTBziOE+lIPX3LJBwM/GB9zn1s=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=zKUdbp4x+/VqA3kL09YPHo90ssi53bgpWiB0pmCwutFAhP4AVF2M351xR9X6fOqno Qc+VmTiirsz48Gs9MHziL7+mu6t7YznscDank/srkzceo/cAtQgosZq7ePaBSY9W8b STS+RiEV9COpiuAiELuhXFCXJ7IjCHlNUSvLFaiM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Catalin Marinas , Ido Schimmel , Ido Schimmel , Robin Murphy , Joerg Roedel , Will Deacon , Andrew Morton , Sasha Levin Subject: [PATCH 6.12 307/337] kmemleak: iommu/iova: fix transient kmemleak false positive Date: Fri, 7 Aug 2026 16:38:30 +0200 Message-ID: <20260807143425.181571712@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807143418.516897842@linuxfoundation.org> References: <20260807143418.516897842@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Catalin Marinas [ Upstream commit 7591c127f3b17d5879f18819cad7058bf3a2e276 ] 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 Stable-dep-of: 79c37ae3733e ("mm/kmemleak: fix checksum computation for per-cpu objects") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- Documentation/dev-tools/kmemleak.rst | 1 drivers/iommu/iova.c | 6 +++++ include/linux/kmemleak.h | 4 +++ mm/kmemleak.c | 39 +++++++++++++++++++++++++++++++++++ 4 files changed, 50 insertions(+) --- a/Documentation/dev-tools/kmemleak.rst +++ b/Documentation/dev-tools/kmemleak.rst @@ -161,6 +161,7 @@ See the include/linux/kmemleak.h header - ``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 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -6,6 +6,7 @@ */ #include +#include #include #include #include @@ -673,6 +674,11 @@ static struct iova_magazine *iova_depot_ { struct iova_magazine *mag = rcache->depot; + /* + * As the mag->next pointer is moved to rcache->depot and reset via + * the mag->size assignment, mark it as a transient false positive. + */ + kmemleak_transient_leak(mag->next); rcache->depot = mag->next; mag->size = IOVA_MAG_SIZE; rcache->depot_size--; --- a/include/linux/kmemleak.h +++ b/include/linux/kmemleak.h @@ -26,6 +26,7 @@ extern void kmemleak_free_part(const voi extern void kmemleak_free_percpu(const void __percpu *ptr) __ref; extern void kmemleak_update_trace(const void *ptr) __ref; extern void kmemleak_not_leak(const void *ptr) __ref; +extern void kmemleak_transient_leak(const void *ptr) __ref; extern void kmemleak_ignore(const void *ptr) __ref; extern void kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp) __ref; extern void kmemleak_no_scan(const void *ptr) __ref; @@ -93,6 +94,9 @@ static inline void kmemleak_update_trace static inline void kmemleak_not_leak(const void *ptr) { } +static inline void kmemleak_transient_leak(const void *ptr) +{ +} static inline void kmemleak_ignore(const void *ptr) { } --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -951,6 +951,28 @@ static void make_black_object(unsigned l } /* + * Reset the checksum of an object. The immediate effect is that it will not + * be reported as a leak during the next scan until its checksum is updated. + */ +static void reset_checksum(unsigned long ptr) +{ + unsigned long flags; + struct kmemleak_object *object; + + object = find_and_get_object(ptr, 0); + if (!object) { + kmemleak_warn("Not resetting the checksum of an unknown object at 0x%08lx\n", + ptr); + return; + } + + raw_spin_lock_irqsave(&object->lock, flags); + object->checksum = 0; + raw_spin_unlock_irqrestore(&object->lock, flags); + put_object(object); +} + +/* * Add a scanning area to the object. If at least one such area is added, * kmemleak will only scan these ranges rather than the whole memory block. */ @@ -1219,6 +1241,23 @@ void __ref kmemleak_not_leak(const void EXPORT_SYMBOL(kmemleak_not_leak); /** + * kmemleak_transient_leak - mark an allocated object as transient false positive + * @ptr: pointer to beginning of the object + * + * Calling this function on an object will cause the memory block to not be + * reported as a leak temporarily. This may happen, for example, if the object + * is part of a singly linked list and the ->next reference to it is changed. + */ +void __ref kmemleak_transient_leak(const void *ptr) +{ + pr_debug("%s(0x%px)\n", __func__, ptr); + + if (kmemleak_enabled && ptr && !IS_ERR(ptr)) + reset_checksum((unsigned long)ptr); +} +EXPORT_SYMBOL(kmemleak_transient_leak); + +/** * kmemleak_ignore - ignore an allocated object * @ptr: pointer to beginning of the object *