From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793808460; b=CGmjfgr5scXmXdxCy5b6yBGZpIIqSXLmI0zP1ErG3OZzY801gk/6c0gHj/Cs/Iiyk4+p F2Ejm7de8jtPKOaW8BJyZrP9LWzqVXUfLqdYhw6DIy9iiku0Cb89HlfiCQWOZQVcvvowN yT+wic9X7XAz94n7bxTMDZ0w/V6nbTHD5gGAtPTN/0/k5d5vYmLKnR2Oe6VG1fpMZkWUg P+fJxy5USlIcf1UdmO7/9QiqA+uHQIV4u/JY8vQr2jo9/57sGV4bZxbJARaBUuLpjFRxZ 3hdlzDWxP0z9rzzWlYBNazNrC4E+vffHZMOkhDqO1AZUb3vmoZFYY8DiVKkGfVS3pJw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793808460; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=jAQE6XsGNYs4FRrRUOdVXVIOk2qnYo6/djLUL1uif54=; b=ORlADLDbcFjaV7PeszvkK9+i4Tkn8mVuVVNSrJV9VUXGSnBEZNYcZAkKEwTZvfARJcX7 qOUu2rvtjKbuYYDNpJd8gyBe1fI6Xn0lEsgcilDALIVdFbFPpKjH8MBOSPf+G6qUk8Gew ptiDTe8m1HHAQ24SnqZwLe5AvqgKsPNy7743qKg14kEoYnp273UULqaV55ixWf2C8+1yK u96wM5gH6vBFGVVQxb38l8ht8ddVJZHLhdhyl9v3AzyTdCxvBCmFcisZqsxG4WvPlTPwL aA2VSJkPG0T8dkBSSD73Tbh6Bxc2cl+nYNk+fluCTWktMB8HF+tm91amWMeBg7F7dxQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Jtpbcmbm; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B97A1606A31B for ; Wed, 4 Nov 2026 16:07:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Jtpbcmbm Received: by smtp.kernel.org (Postfix) with ESMTPSA id 351241F000C1; Wed, 4 Nov 2026 16:07:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793808459; bh=jAQE6XsGNYs4FRrRUOdVXVIOk2qnYo6/djLUL1uif54=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=JtpbcmbmFpOB9+9KnsfGyq8bWt+Nw1MfGMJYN00bFBXw+ZRE/yJaxWsVkqzd8Rt3/ 4d2PayILvz+VIaL4WVG2SMrB+fn5HlOHyh3DLAGYbkjzogyOOO6LAtv1n9IJomKmsS 6VhsD5pY0cHcom3nfzzcGF6h+ccGbFMn2zqj+6oPe9SkPpmRd6zXaZFTicbqAUcB/G D1kxhv5nnwqUmlfx7HpwxFyZJmXzk9ZpiuG3Zycme7jNNHvvx+4NSGRUCti46aK3Tq WnrcRuvZat/Fgm2H34tKHv/wqWR8UpIjR977s/WXvEt3MiwPKvW02IOZrtfR0pEBWA eFLJnvdTcQs+Q== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH 2/4] software node: use kobject_get_unless_zero() in software_node_find_by_name() Reply-To: sashiko-reviews@lists.linux.dev To: =?utf-8?b?UGVuZyBGYW4gKE9TUyk=?= Cc: imx@lists.linux.dev, Frank.Li@kernel.org In-Reply-To: <20261104-swnode-race-v1-v1-2-9406a67e25be@nxp.com> References: <20261104-swnode-race-v1-v1-0-9406a67e25be@nxp.com> <20261104-swnode-race-v1-v1-2-9406a67e25be@nxp.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Wed, 04 Nov 2026 16:07:38 +0000 X-Mailing-List: imx@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Thank you for your contribution! Sashiko AI review found 2 potential issue(= s) to consider: - [High] software node: use-after-free on swnode->node in software_node_fin= d_by_name() - [Low] software node: wrong Fixes tag for software_node_find_by_name() -- commit e919f34826aef89486e543d4a209837a0357d8a1 Author: Peng Fan software node: use kobject_get_unless_zero() in software_node_find_by_name() This commit updates software_node_find_by_name() to use kobject_get_unless_zero() instead of swnode_get() so that it skips entries = in swnode_kset->list whose reference count has already dropped to zero. > software node: use kobject_get_unless_zero() in software_node_find_by= _name() > =20 > software_node_find_by_name() also walks the swnode kset list and take= s a > reference with swnode_get(). Like the pointer-based lookup, it can > encounter an entry whose refcount has already reached zero but which = is > still linked until its delayed release callback runs. > =20 > Use kobject_get_unless_zero() and continue scanning when the entry is > already dying. > =20 > Fixes: 80488a6b1d3c ("software node: Add support for static node desc= riptors") > Signed-off-by: Peng Fan [Severity: Low] Commit 80488a6b1d3c ("software node: Add support for static node descriptors") introduced software_node_to_swnode(), while software_node_find_by_name() was added later. Should the Fixes tag instead reference the commit that introduced software_node_find_by_name()? Fixes: 1666faedb567 ("software node: Add software_node_find_by_name()") > diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c > index 19a4153f3fac1..9095d50ba146f 100644 > --- a/drivers/base/swnode.c > +++ b/drivers/base/swnode.c > @@ -831,8 +831,8 @@ software_node_find_by_name(const struct software_node= *parent, const char *name) > swnode =3D kobj_to_swnode(k); > if (parent =3D=3D swnode->node->parent && swnode->node->name && > !strcmp(name, swnode->node->name)) { > - swnode_get(swnode); > - break; > + if (kobject_get_unless_zero(k)) > + break; > } [Severity: High] Can dereferencing swnode->node->parent and swnode->node->name before calling kobject_get_unless_zero(k) cause a use-after-free when scanning past a dying swnode? When a software node is registered via software_node_register(), software_node_register_node_group(), or device_add_software_node(), swnode->allocated is 0 and swnode->node points directly to caller-owned memory rather than an internal copy freed in software_node_release(): drivers/base/swnode.c:software_node_release() { ... if (swnode->allocated) software_node_free(swnode->node); ... } Once software_node_unregister() drops swnode->kobj.kref to zero and returns, the caller can immediately free or unmap the backing struct software_node while the dying swnode remains on swnode_kset->list awaiting kobject cleanup (for example when CONFIG_DEBUG_KOBJECT_RELEASE delays release, or before kset_leave() acquires swnode_kset->list_lock). For instance, ipu_bridge_init() in drivers/media/pci/intel/ipu-bridge.c unregisters a heap-allocated node and immediately frees it: err_unregister_ipu: software_node_unregister(&bridge->ipu_hid_node); err_free_bridge: kfree(bridge); Similarly, fwnode_pointer() in lib/tests/printf_kunit.c registers stack-allocated software_node structures and unregisters them right before returning from the stack frame. Should software_node_find_by_name() acquire the reference via kobject_get_unless_zero(k) before dereferencing swnode->node, and drop that reference if the parent or name does not match? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261104-swnode-rac= e-v1-v1-0-9406a67e25be@nxp.com?part=3D2