From nobody Mon Sep 28 07:17:05 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 947A13A6EE9; Tue, 25 Aug 2026 05:21:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787635293; cv=none; b=TIv4QtZqUnwfZfNgkxIUxu8FBXnTIeKgOkpu0x20oKL5DIqx+SIot05m/rStS98XJ0wiNvFMvobRYZw91Tn1GakmX2hPo4EPkSmebkP/boFj7Pfd2fLPnpQKCUqd1AD/H1wrUcvn/NrpHhyPGXSzUP+bwllM1q4KOMIznvPfm8Q= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787635293; c=relaxed/simple; bh=O0UzbZAN0EpcTXAFz5ooHMP36tBWRVlQCm0SfHy87J4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=mfnSkisZgHMe2/M2o9xS4i97kmCNRvhEU5uNqjUQurUNU1dCspCLIS91agQav0gfL0axSUOac3bKvNLuBD4F4Gn72dhbaiYZMgQrGararHYwqyQfy5YlAUrcKuIXO8+/KGB5Sp/pfIdbaQlCzNwVFs5fxsMbN/2E5A7sej57IGs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=D/HsFukf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="D/HsFukf" Received: by smtp.kernel.org (Postfix) with ESMTPS id 3A587C2BCFA; Tue, 25 Aug 2026 05:21:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1787635293; bh=O0UzbZAN0EpcTXAFz5ooHMP36tBWRVlQCm0SfHy87J4=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=D/HsFukf1XoOa3vf9YTdmOJD+vyOEoj6hK+NOunVkfj4e67efdz+m543FQeSIYtJO HeHlMrtI/2A91MG+uFq/yxDdV2aAx9NHKbRBZBsw/5aZynuEswp6ivB+WSApvlqCTm 1Igk9l1hMn6cDXHC6IufXY8UtlyUEcuAByH+UjvUUHMwA321SEU6fqTjyknAbaOkek leslUHjblA7L/pcpHY90JJNN5ilIv/JtQnBphKn3ZGjAXxk0/T31Ilf+HSQspRoz+4 VbfvuHi20cTs7lxOE1kss4GwRX57Y9yeFLZim8iq0k0+xsKznvsCMMl9UMgrYap4xc 7OeAGQokuXHXA== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B340C5DF94; Tue, 25 Aug 2026 05:21:33 +0000 (UTC) From: Ivan Immanuel Shaji via B4 Relay Date: Tue, 25 Aug 2026 01:20:37 -0400 Subject: [PATCH 1/2] tracing: Fix retry exhaustion in simple ring buffer reader swap Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260825-kernel-patch-1-v1-1-e9349aa0b165@gmail.com> References: <20260825-kernel-patch-1-v1-0-e9349aa0b165@gmail.com> In-Reply-To: <20260825-kernel-patch-1-v1-0-e9349aa0b165@gmail.com> To: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Vincent Donnefort Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, stable@vger.kernel.org, Ivan Immanuel Shaji X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1787635292; l=1613; i=ivanimmanuel1234@gmail.com; s=20260825; h=from:subject:message-id; bh=GwccFW1nTWWYVnS3r35/SqG9HHBPVSmi0y6pEIwL9rA=; b=uphKKVL9amV7PgkCBG78fcuiBHKszcd+IQnJm6N6imNxYSqSFjW0vwTnoty5JsRCaN+r3ZGwA hLb8upGLaUzDg7I6ayMuYbEt9x+WwgrYYSbp8LSL6urpX6uVbt5TdMF X-Developer-Key: i=ivanimmanuel1234@gmail.com; a=ed25519; pk=Wx8O3UUs3XneDkbqbOJJnlNdWSpEf2tWbTAoE7/vnqE= X-Endpoint-Received: by B4 Relay for ivanimmanuel1234@gmail.com/20260825 with auth_id=975 X-Original-From: Ivan Immanuel Shaji Reply-To: ivanimmanuel1234@gmail.com From: Ivan Immanuel Shaji simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. The current !retry test reverses both outcomes. It returns an error after a successful final replacement, leaving the link update complete but the reader bookkeeping unfinished. After a failed final replacement, it falls through and updates the head and reader pointers as though the replacement succeeded, which can corrupt the ring. Treat only a negative counter as exhaustion and return the documented -EBUSY error. Fixes: 34e5b958bdad ("tracing: Introduce simple_ring_buffer") Cc: stable@vger.kernel.org Assisted-by: LLM sparse Signed-off-by: Ivan Immanuel Shaji Reviewed-by: Vincent Donnefort --- kernel/trace/simple_ring_buffer.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_b= uffer.c index f4642f5adda3..49913bb0057a 100644 --- a/kernel/trace/simple_ring_buffer.c +++ b/kernel/trace/simple_ring_buffer.c @@ -160,8 +160,8 @@ int simple_ring_buffer_swap_reader_page(struct simple_r= b_per_cpu *cpu_buffer) overrun =3D cpu_buffer->meta->overrun; } while (!simple_bpage_unset_head_link(last, reader, SIMPLE_RB_LINK_NORMA= L) && retry--); =20 - if (!retry) - return -EINVAL; + if (retry < 0) + return -EBUSY; =20 cpu_buffer->head_page =3D simple_bpage_from_link(reader->link.next); cpu_buffer->head_page->link.prev =3D &reader->link; --=20 2.53.0 From nobody Mon Sep 28 07:17:05 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7407936308A; Tue, 25 Aug 2026 05:21:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787635293; cv=none; b=NrZYWTdrHtONU5mS925BLWcuThBTsOaFirGDFQEl4e19PHiYLTcMd/mPsIzIUNKhyeX5XVtFo7vlvCVVQUdoTk/zD/VXLSE6dpsHW+D5y1emaF0IA/FgIX7Ag/QpAuK7euBXM7G5M0aKFfVeKnMblVVv8HqsUtRGiKAO/09j7Y0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787635293; c=relaxed/simple; bh=6Y1XbZWfQiu+oywBa1EwFn9wtGU0Z1a2BMaPr+MkY/U=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Oen7WB8B0NLxKvnoHCxHMPY7b2AoUS3znFwReQaIijK5YGSlFiOI/Ed+cCSCJ5dm8BA/taNzvWAZ7b/VPn+TahQ5H/p+66Fb25XL22MfHwuCKqia5rkOAZqNap4rauC9PJJsJQ7aqNFOa034+4ATkS6lfzQfTWKisPsiOtURKrU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=shmbcStw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="shmbcStw" Received: by smtp.kernel.org (Postfix) with ESMTPS id 464F8C2BCFB; Tue, 25 Aug 2026 05:21:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1787635293; bh=6Y1XbZWfQiu+oywBa1EwFn9wtGU0Z1a2BMaPr+MkY/U=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=shmbcStwdzlHkU1pz/DI2vV39TmrISx9lmIQrhIfUmUx/y/qLodk9wiYX96kxKGvB nobQLcSIyb7/KOr1JSD4u6K60xTmg43z+/6OgwF+4MW63MHdWfZ03l1WezOG/qiHy3 xVgWRTfMzHT2BvfEm7+/NE/AoPqxvkAimXBV1m4fxifvVV1do9PikYOBWRi84YiwgH E9eulQP0H5nywd9RMIvmN5ysSli0to8x5fmkQ7hjUDs0WmjXTxLO4b7mddN8mV/vvU tAwEzu7EagndrRIn0lJ40Rk0PNGsZJuvvzgmNuJAdkWFwbl11Eh90rYRP0Z6ETxUBE VuYprDepuR04g== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2A853C61DB6; Tue, 25 Aug 2026 05:21:33 +0000 (UTC) From: Ivan Immanuel Shaji via B4 Relay Date: Tue, 25 Aug 2026 01:20:38 -0400 Subject: [PATCH 2/2] ring-buffer: Stop remote reader update when page swap fails Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260825-kernel-patch-1-v1-2-e9349aa0b165@gmail.com> References: <20260825-kernel-patch-1-v1-0-e9349aa0b165@gmail.com> In-Reply-To: <20260825-kernel-patch-1-v1-0-e9349aa0b165@gmail.com> To: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Vincent Donnefort Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, stable@vger.kernel.org, Ivan Immanuel Shaji X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1787635292; l=1498; i=ivanimmanuel1234@gmail.com; s=20260825; h=from:subject:message-id; bh=Yt3jJEKjDX8/on3DO9yN+/vqaXIqohP/+YVJCaaE2TA=; b=KmTfJ3GvG/u3YrBfBZAyX5nOKK+yVn9H2LRQsIdURBZL6eyXNJKeUDzGR4U1N8WGLf9D7C5OU bnWoYbWgI93DAs3LZpK+WUo1uq3qAEUUgZNrxB3zqY9axeBmdR+8JnZ X-Developer-Key: i=ivanimmanuel1234@gmail.com; a=ed25519; pk=Wx8O3UUs3XneDkbqbOJJnlNdWSpEf2tWbTAoE7/vnqE= X-Endpoint-Received: by B4 Relay for ivanimmanuel1234@gmail.com/20260825 with auth_id=975 X-Original-From: Ivan Immanuel Shaji Reply-To: ivanimmanuel1234@gmail.com From: Ivan Immanuel Shaji The remote swap_reader_page callback can fail when the writer moves the head before the remote catches it. __rb_get_reader_page_from_remote() warns about that failure but continues with the unchanged reader ID and rearranges the local page list as though the swap succeeded. Stop immediately after warning. Callers already handle a NULL reader page as a failed attempt, and this avoids splicing the same page as both the previous and new reader. Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes") Cc: stable@vger.kernel.org Assisted-by: LLM sparse Signed-off-by: Ivan Immanuel Shaji --- kernel/trace/ring_buffer.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 3c3ed639923d..d11b2759caac 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -5805,8 +5805,9 @@ __rb_get_reader_page_from_remote(struct ring_buffer_p= er_cpu *cpu_buffer) =20 prev_reader =3D cpu_buffer->subbuf_ids[cpu_buffer->meta_page->reader.id]; =20 - WARN_ON_ONCE(cpu_buffer->remote->swap_reader_page(cpu_buffer->cpu, - cpu_buffer->remote->priv)); + if (WARN_ON_ONCE(cpu_buffer->remote->swap_reader_page(cpu_buffer->cpu, + cpu_buffer->remote->priv))) + return NULL; /* nr_pages doesn't include the reader page */ if (WARN_ON_ONCE(cpu_buffer->meta_page->reader.id > cpu_buffer->nr_pages)) return NULL; --=20 2.53.0