From patchwork Tue Feb 27 17:57:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13574249 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 01EC91419B3; Tue, 27 Feb 2024 17:55:05 +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=1709056506; cv=none; b=k5KBGQxzmQI5uHaUPD1qbkzYYL5PUK/0UnVAWovlR2As8C6xfdC8d7msK5MtMwdvgzpYcnM7vky77GPwJStiFQWl3YHS2UsoGHH4gV0/gI2a2j871RrBIFESW7BH0xt+d8DOdKKtsTAnjXeWPUHyow6iyNcLsHpqPvUozEArW6E= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709056506; c=relaxed/simple; bh=fEAAGW+WyZIqxwlQgw3mUs/pzzZX+uujTliQ839XUuA=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=cNhgRKMW4YLxEh6DcOTpmFfeB1WBs3Ufs8B3R9MFD3i8upSkiKlLlxZMBiHOSdld1G/zQba+eiEXdA9aEOvOubhRKToRanfe9geJ4SXBE8Fq5ZmXkLNRC5/ZdA55eCOUe+SIuA9PcViiVUWqPsSou41t31u/Jim82MhtVlBETe4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id A28FFC433F1; Tue, 27 Feb 2024 17:55:04 +0000 (UTC) Date: Tue, 27 Feb 2024 12:57:06 -0500 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mathieu Desnoyers , Sachin Sant Subject: [PATCH] tracing: Prevent trace_marker being bigger than unsigned short Message-ID: <20240227125706.04279ac2@gandalf.local.home> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Steven Rostedt (Google)" The trace_marker write goes into the ring buffer. A test was added to write a string as big as the sub-buffer of the ring buffer to see if it would work. A sub-buffer is typically PAGE_SIZE in length. On PowerPC architecture, the ftrace selftest for trace_marker started to fail. This was due to PowerPC having a PAGE_SIZE of 65536 and not 4096. It would try to write a string that was around 63000 bytes in size. This gave the following warning: ------------[ cut here ]------------ precision 63492 too large WARNING: CPU: 15 PID: 2538829 at lib/vsprintf.c:2721 set_precision+0x68/0xa4 Modules linked in: CPU: 15 PID: 2538829 Comm: awk Tainted: G M O K 6.8.0-rc5-gfca7526b7d89 #1 Hardware name: IBM,9080-HEX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1060.00 (NH1060_018) hv:phyp pSeries NIP: c000000000f57c34 LR: c000000000f57c30 CTR: c000000000f5cdf0 REGS: c000000a58e4f5f0 TRAP: 0700 Tainted: G M O K (6.8.0-rc5-gfca7526b7d89) MSR: 8000000002029033 CR: 48000824 XER: 00000005 CFAR: c00000000016154c IRQMASK: 0 GPR00: c000000000f57c30 c000000a58e4f890 c000000001482800 0000000000000019 GPR04: 0000000100011559 c000000a58e4f660 c000000a58e4f658 0000000000000027 GPR08: c000000e84e37c10 0000000000000001 0000000000000027 c000000002a47e50 GPR12: 0000000000000000 c000000e87bf7300 0000000000000000 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR20: c0000004a43ec590 0000000000400cc0 0000000000000003 c0000000012c3e65 GPR24: c000000a58e4fa18 0000000000000025 0000000000000020 000000000001ff97 GPR28: c0000001168a00dd c0000001168c0074 c000000a58e4f920 000000000000f804 NIP [c000000000f57c34] set_precision+0x68/0xa4 LR [c000000000f57c30] set_precision+0x64/0xa4 Call Trace: [c000000a58e4f890] [c000000000f57c30] set_precision+0x64/0xa4 (unreliable) [c000000a58e4f900] [c000000000f5ccc4] vsnprintf+0x198/0x4c8 [c000000a58e4f980] [c000000000f53228] seq_buf_vprintf+0x50/0xa0 [c000000a58e4f9b0] [c00000000031cec0] trace_seq_printf+0x60/0xe0 [c000000a58e4f9e0] [c00000000031b5f0] trace_print_print+0x78/0xa4 [c000000a58e4fa60] [c0000000003133a4] print_trace_line+0x2ac/0x6d8 [c000000a58e4fb20] [c0000000003145c0] s_show+0x58/0x2c0 [c000000a58e4fba0] [c0000000005dfb2c] seq_read_iter+0x448/0x618 [c000000a58e4fc70] [c0000000005dfe08] seq_read+0x10c/0x174 [c000000a58e4fd10] [c00000000059a7e0] vfs_read+0xe0/0x39c [c000000a58e4fdc0] [c00000000059b59c] ksys_read+0x7c/0x140 [c000000a58e4fe10] [c000000000035d74] system_call_exception+0x134/0x330 [c000000a58e4fe50] [c00000000000d6a0] system_call_common+0x160/0x2e4 The problem was that in trace_print_print() that reads the trace_marker write data had the following code: int max = iter->ent_size - offsetof(struct print_entry, buf); [..] trace_seq_printf(s, ": %.*s", max, field->buf); Where "max" was the size of the entry. Now that the write to trace_marker can be as big as what the sub-buffer can hold, and the sub-buffer for powerpc is 64K in size, the "max" value was: 63492, and that was passed to trace_seq_printf() which eventually calls vsnprintf() with the same format and parameters. The max "precision" that "%.*s" can be is max signed short (32767) where 63492 happens to be greater than. Prevent the max size written by trace_marker to be greater than what a signed short can hold. Link: https://lore.kernel.org/all/C7E7AF1A-D30F-4D18-B8E5-AF1EF58004F5@linux.ibm.com/ Reported-by: Sachin Sant Tested-by: Sachin Sant Fixes: 8ec90be7f15f ("tracing: Allow for max buffer data size trace_marker writes") Signed-off-by: Steven Rostedt (Google) Acked-by: Masami Hiramatsu (Google) --- kernel/trace/trace.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8198bfc54b58..1606fa99367b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7310,7 +7310,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, /* Used in tracing_mark_raw_write() as well */ #define FAULTED_STR "" #define FAULTED_SIZE (sizeof(FAULTED_STR) - 1) /* '\0' is already accounted for */ - +#ifndef SHORT_MAX +#define SHORT_MAX ((1<<15) - 1) +#endif if (tracing_disabled) return -EINVAL; @@ -7328,6 +7330,16 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, if (cnt < FAULTED_SIZE) size += FAULTED_SIZE - cnt; + /* + * trace_print_print() uses vsprintf() to determine the size via + * the precision format "%.*s" which can not be greater than + * a signed short. + */ + if (size > SHORT_MAX) { + cnt -= size - SHORT_MAX; + goto again; + } + if (size > TRACE_SEQ_BUFFER_SIZE) { cnt -= size - TRACE_SEQ_BUFFER_SIZE; goto again;