From nobody Sat Feb 7 15:48:16 2026 Received: from mail-oo1-f70.google.com (mail-oo1-f70.google.com [209.85.161.70]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0C34231DDB8 for ; Fri, 30 Jan 2026 15:09:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.70 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769785773; cv=none; b=dhEvM5eKc0nnacjEATbpnAoGKDB7r80Pdl1ppVz9qSKgc2f4E3MhCdl1U2XfvK13nBLpYhdxSHXleahjvhbsvySBBdrDiqxifD7w+GlBIEh4svqAU4sDE17GgXg+Jx7I1d6Ljc5/oMnBJ5i6uLPzO5tdsqlFh3H/5z/MSF7GQm4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769785773; c=relaxed/simple; bh=QBI0QMtyb/dH+jgccuBOIHLTSYM7czmrg3211IErhkA=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=Roiazm5BiMxnN1nN1UH+0NzTV1Qp6oKOpG62WBtmAXdAuhZCnceulHVUg/hGGBWcT/q5s/hY3oPtGceqP5MjDLnRPEwwGYy1g0q4vUcW5P6QAmQ1tNWdVFscHkgoGKaVG//zMl9WxOVLfaG3zLO2Dz76YEz+vGBNUzuRsswO8bc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.161.70 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oo1-f70.google.com with SMTP id 006d021491bc7-6630b0a016aso5312399eaf.0 for ; Fri, 30 Jan 2026 07:09:31 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769785771; x=1770390571; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Zku2tTZCrYzIn+fXZApbZQK2N5cogEt0jvnmUuKEzHc=; b=N8fuy+xedo5uOOePELFomPCqmbifW+8yR/gDg2pvmtXJy0JFSCn7uDDtmVaXRiORBw S+44IL4QthvFrETzK7V2q+NBryywn7fP4+dUv8CNNrCnISrmcBuNvRmlvaplCo6JUPmv oaUUIFiXNC8RyigA/d/CZDl/p8qxkuXZHvgBP2Qy3DunSAx5BD9Hf/SvOtye+AMr+Un0 hjKZSUIq34DE+CypwhhHn8nZRZuJJUrECz69nM0ZwIzx3DOVlFXYA+qKm2hglxkWvP7S HU+yS2UMlNB8cbnqP5RA6Zoe83OLTH/XC0kjQxYqay5XXsgqJKftbZ8wSVay+yaKEAXz kvVA== X-Gm-Message-State: AOJu0Yy1QhaodaEueQPWy8X/yO2B/zs1i9+LfGWzb4hRkzHo/+GUUX3H 8bFcqbyvl4qp8PcT7Z91cse9ztXCWQeMm/v1IvGKC+AvNaWMQcRLId3wsWv080QkTZK6yM8GrhX 2qUHWH8SF44fZxv1tz1qYHXIzT+ybtEvOHJbmdTEeJWHP8uOxFPjoMZdKau4= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:3109:b0:663:888:6093 with SMTP id 006d021491bc7-6630f3956fcmr1667460eaf.70.1769785771015; Fri, 30 Jan 2026 07:09:31 -0800 (PST) Date: Fri, 30 Jan 2026 07:09:30 -0800 In-Reply-To: <697be614.a70a0220.8545c.0069.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <697cc9aa.050a0220.371857.00e4.GAE@google.com> Subject: Forwarded: [PATCH v2] tracing/dma: Cap dma_map_sg tracepoint arrays to prevent buffer overflow From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: [PATCH v2] tracing/dma: Cap dma_map_sg tracepoint arrays to preven= t buffer overflow Author: kartikey406@gmail.com #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git= master The dma_map_sg tracepoint can trigger a perf buffer overflow when tracing large scatter-gather lists. With devices like virtio-gpu creating large DRM buffers, nents can exceed 1000 entries, resulting in: phys_addrs: 1000 * 8 bytes =3D 8,000 bytes dma_addrs: 1000 * 8 bytes =3D 8,000 bytes lengths: 1000 * 4 bytes =3D 4,000 bytes Total: ~20,000 bytes This exceeds PERF_MAX_TRACE_SIZE (8192 bytes), causing: WARNING: CPU: 0 PID: 5497 at kernel/trace/trace_event_perf.c:405 perf buffer not large enough, wanted 24620, have 8192 Cap all three dynamic arrays at 128 entries using min() in the array size calculation. This ensures arrays are only as large as needed (up to the cap), avoiding unnecessary memory allocation for small operations while preventing overflow for large ones. The tracepoint now records the full nents/ents counts and a truncated flag so users can see when data has been capped. Changes in v2: - Use min(nents, DMA_TRACE_MAX_ENTRIES) for dynamic array sizing instead of fixed DMA_TRACE_MAX_ENTRIES allocation (feedback from Steven Rostedt) - This allocates only what's needed up to the cap, avoiding waste for small operations Reported-by: syzbot+28cea38c382fd15e751a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D28cea38c382fd15e751a Signed-off-by: Deepanshu Kartikey --- include/trace/events/dma.h | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h index b3fef140ae15..33e99e792f1a 100644 --- a/include/trace/events/dma.h +++ b/include/trace/events/dma.h @@ -275,6 +275,8 @@ TRACE_EVENT(dma_free_sgt, sizeof(u64), sizeof(u64))) ); =20 +#define DMA_TRACE_MAX_ENTRIES 128 + TRACE_EVENT(dma_map_sg, TP_PROTO(struct device *dev, struct scatterlist *sgl, int nents, int ents, enum dma_data_direction dir, unsigned long attrs), @@ -282,9 +284,12 @@ TRACE_EVENT(dma_map_sg, =20 TP_STRUCT__entry( __string(device, dev_name(dev)) - __dynamic_array(u64, phys_addrs, nents) - __dynamic_array(u64, dma_addrs, ents) - __dynamic_array(unsigned int, lengths, ents) + __field(int, full_nents) + __field(int, full_ents) + __field(bool, truncated) + __dynamic_array(u64, phys_addrs, min(nents, DMA_TRACE_MAX_ENTRIES)) + __dynamic_array(u64, dma_addrs, min(ents, DMA_TRACE_MAX_ENTRIES)) + __dynamic_array(unsigned int, lengths, min(ents, DMA_TRACE_MAX_ENTRIES)) __field(enum dma_data_direction, dir) __field(unsigned long, attrs) ), @@ -292,11 +297,16 @@ TRACE_EVENT(dma_map_sg, TP_fast_assign( struct scatterlist *sg; int i; + int traced_nents =3D min_t(int, nents, DMA_TRACE_MAX_ENTRIES); + int traced_ents =3D min_t(int, ents, DMA_TRACE_MAX_ENTRIES); =20 __assign_str(device); - for_each_sg(sgl, sg, nents, i) + __entry->full_nents =3D nents; + __entry->full_ents =3D ents; + __entry->truncated =3D (nents > DMA_TRACE_MAX_ENTRIES) || (ents > DMA_TR= ACE_MAX_ENTRIES); + for_each_sg(sgl, sg, traced_nents, i) ((u64 *)__get_dynamic_array(phys_addrs))[i] =3D sg_phys(sg); - for_each_sg(sgl, sg, ents, i) { + for_each_sg(sgl, sg, traced_ents, i) { ((u64 *)__get_dynamic_array(dma_addrs))[i] =3D sg_dma_address(sg); ((unsigned int *)__get_dynamic_array(lengths))[i] =3D @@ -306,9 +316,12 @@ TRACE_EVENT(dma_map_sg, __entry->attrs =3D attrs; ), =20 - TP_printk("%s dir=3D%s dma_addrs=3D%s sizes=3D%s phys_addrs=3D%s attrs=3D= %s", + TP_printk("%s dir=3D%s nents=3D%d/%d ents=3D%d/%d%s dma_addrs=3D%s sizes= =3D%s phys_addrs=3D%s attrs=3D%s", __get_str(device), decode_dma_data_direction(__entry->dir), + min_t(int, __entry->full_nents, DMA_TRACE_MAX_ENTRIES), __entry->full_ne= nts, + min_t(int, __entry->full_ents, DMA_TRACE_MAX_ENTRIES), __entry->full_ent= s, + __entry->truncated ? " [TRUNCATED]" : "", __print_array(__get_dynamic_array(dma_addrs), __get_dynamic_array_len(dma_addrs) / sizeof(u64), sizeof(u64)), --=20 2.43.0