From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (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 572DA33F5A4; Fri, 29 May 2026 07:45:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780040731; cv=none; b=YJT+9OOyS4K377QAKAFk2eBqp9LhjipP5S4goHrlkWjLslVAkc2ofhJRTOmsG5GnEgvz3bRfjDYSyhkgFSTEhsiqXsx/KaO33bqCkIG17O8AVKzNg9fyq/gjF9dzTu5Hw+PUWqazQmwe8LfwJbeTChDbyOtfBP8CGm44bUUBdWM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780040731; c=relaxed/simple; bh=mEM95G3WNy6plziLguYpsnPOf7PAIL0711uhgZK4fMw=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=cxdRGKQT4O4M62I9yU7V6TayjVHAXlbGitU3Cn1WMPSQSkViu24EiiHBdTfulbC/MwerQ/LTcrqiY2rp9ScMhcVSYXXw1ypYo86sZrLgFOJ5fnHxaZcuKEcmd9SM81nlnX7bORzbytevxR46YM/bXfKPbcKSc5b1Siod4400QKU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org; spf=pass smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=F237WIcV; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="F237WIcV" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:Cc:To:In-Reply-To:References: Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description; bh=Y2P1ayzVY7FwXmEpq+5FJne3BKpnMFMzUXsWtT6mEVY=; b=F237WIcV+KEddYQm8+bL3fQgQm YfiVTG72OVAKiDnUh/A+nhE/5LANGS3glUsyWwktOhew4/SqZ3JiO/KdgxOAcaDGHDHzYSDcoiX7x vyQSR7J8O0U2PHTz0sx4dwCZhKDDLtsrz0ITkTzq1D5d3AgHKB+/trLpnvcYhqjBo2NUGHZSPAh7j maUqdLGkB/O2o6nABbkEb91B3ZVjE8wDZXIumyGcpIwWRzaLpfETy3fEhjKgKPN1UhHU/Ysg5vUSQ JQre4Vq5UGDjLgyONoyVI24szXvquoHsbKBMGyMnWWvIdLHf083Q/iaQYjyfK45TWu5ZPAw4+ez12 bdrPnfvA==; Received: from authenticated-user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1wSruD-004kM5-1g; Fri, 29 May 2026 07:45:21 +0000 From: Breno Leitao Date: Fri, 29 May 2026 03:45:12 -0400 Subject: [PATCH net 2/3] netconsole: do not dequeue pooled skbs that cannot satisfy len 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: 7bit Message-Id: <20260529-netcons_fix_before_move-v1-2-cb2d1426dd75@debian.org> References: <20260529-netcons_fix_before_move-v1-0-cb2d1426dd75@debian.org> In-Reply-To: <20260529-netcons_fix_before_move-v1-0-cb2d1426dd75@debian.org> To: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Neil Horman , Cong Wang Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Breno Leitao , kernel-team@meta.com X-Mailer: b4 0.16-dev-d5d98 X-Developer-Signature: v=1; a=openpgp-sha256; l=4366; i=leitao@debian.org; h=from:subject:message-id; bh=mEM95G3WNy6plziLguYpsnPOf7PAIL0711uhgZK4fMw=; b=owEBbQKS/ZANAwAKATWjk5/8eHdtAcsmYgBqGUQMSS85VJvrhxKGQlisDTMktYQdRMPcdjnHI qZRT0b01mSJAjMEAAEKAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCahlEDAAKCRA1o5Of/Hh3 bfp1EACPmTE08kNbFONb4I4Gr8l+veHNfFq7Tg4A8uyIaxgk50m5PCVvEAhcYZsWHDAWMcSqGU3 /Z3IXKbPe1Fr8R0EInMtREyn+snbQJ3a4I4zCodul0AxJq+0ErjzwyKbvildSLxOVwXomwCi/SS eNbWklgXxRYnP4eh41g3lUGCcAFO1Qqw8rM0f4epezgSMvrt7xEoYotzRjguG3pqYfHfyrJVEXZ ZpYd4XRRZo9FR8h7Iw5LskegTkKFu5u5TfVlR/1EFYYShBkd6yUq12wmiexV0vaZ4CQvauS5ae2 sHRVEA1SeGPqfGiuPRE7rfVnO1ZPehbL5EJTwGbPKaYgT1uCojziUsnwwRhEtGXUvE3knrZjGA6 5ufFsT2/6QTHqXtNGiH1sug+IBq/PjF2kO8vuJUS87THets36/6smIjk8UKa3O3c2yUht8YS2X0 kQ/naZvCVQvmjoB2VCe0tR115k3KJO8ykzNkWni5u3ZQ1e59ZXF1+E1v42AActj0ltAXqb4+j5O C8sdBnKijxUe59xuvMPVCpPbDXHvS02svg3L441o/Q8UgxnRTN5TUMBUJnEhqPtJc7Bs7T1odB2 dfdJikbcW+KKCiQj2sCKI2m2P7S9HCrPikKj9sBULZ7kWQEsfwb29Msts5FvUDVEFRl1UFHeg6Y 24nRM2Hbn34UJNw== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Debian-User: leitao find_skb() falls back to np->skb_pool when the GFP_ATOMIC alloc_skb() fails. The pool is refilled by refill_skbs(), which always allocates buffers of MAX_SKB_SIZE (ethhdr + iphdr + udphdr + MAX_UDP_CHUNK == 1502 bytes). netconsole, however, computes the requested length dynamically as total_len + np->dev->needed_tailroom If the egress device declares a non-zero needed_tailroom (e.g. some tunnel or hardware accelerator devices), the required length can exceed MAX_SKB_SIZE. The pooled skb is then handed back to the caller, which immediately performs skb_put(skb, len), trips the tail > end check, and triggers skb_over_panic(). Leave the normal alloc_skb(len, GFP_ATOMIC) path untouched -- the slab allocator can still satisfy oversized requests when memory is available, so senders to devices with non-zero needed_tailroom keep working in the common case. Only the pool fallback is gated: when alloc_skb() failed and len exceeds the pool buffer size, skip the skb_dequeue() instead of burning a pre-allocated skb on a request that would later trip skb_over_panic(). Reserving pool entries for requests they can actually satisfy also keeps the panic path, which depends on the pool being primed, intact. When that drop happens, emit a rate-limited net_warn() so the user notices that netconsole is unable to push messages on the egress device. The warn is skipped under in_nmi() for the same reason schedule_work() is: printk machinery taken by net_warn_ratelimited() is not NMI-safe and would risk recursing into the same nbcon console we are servicing. MAX_SKB_SIZE / MAX_UDP_CHUNK were private to net/core/netpoll.c. Move them to include/linux/netpoll.h so netconsole can reference the same definition that refill_skbs() uses, keeping the two in sync by construction. The header now pulls in and explicitly so MAX_SKB_SIZE remains self-contained for any future user. Fixes: 954fba027405 ("netpoll: fix netpoll_send_udp() bugs") Signed-off-by: Breno Leitao --- drivers/net/netconsole.c | 7 ++++++- include/linux/netpoll.h | 16 ++++++++++++++++ net/core/netpoll.c | 7 ------- 3 files changed, 22 insertions(+), 8 deletions(-) diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index 699bdfa1fb45..a3dcbe713a0b 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -1680,8 +1680,13 @@ static struct sk_buff *find_skb(struct netpoll *np, int len, int reserve) repeat: skb = alloc_skb(len, GFP_ATOMIC); - if (!skb) + if (!skb) { + /* The pool is refilled with MAX_SKB_SIZE buffers */ + if (WARN_ON_ONCE(len > MAX_SKB_SIZE)) + return NULL; + skb = netcons_skb_pop(np); + } if (!skb) { if (++count < 10) { diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h index e4b8f1f91e54..88f7daa8560e 100644 --- a/include/linux/netpoll.h +++ b/include/linux/netpoll.h @@ -13,12 +13,28 @@ #include #include #include +#include +#include union inet_addr { __be32 ip; struct in6_addr in6; }; +/* + * Maximum payload netpoll's preallocated skb pool can carry. Keep this in + * sync with the buffer size used by refill_skbs() in net/core/netpoll.c; + * callers (e.g. netconsole) use it to detect requests the pool can never + * satisfy and avoid dequeuing a pooled skb that would later trip + * skb_over_panic() in skb_put(). + */ +#define MAX_UDP_CHUNK 1460 +#define MAX_SKB_SIZE \ + (sizeof(struct ethhdr) + \ + sizeof(struct iphdr) + \ + sizeof(struct udphdr) + \ + MAX_UDP_CHUNK) + struct netpoll { struct net_device *dev; netdevice_tracker dev_tracker; diff --git a/net/core/netpoll.c b/net/core/netpoll.c index b3fe59445f2d..229dde818ab3 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -41,16 +41,9 @@ * message gets out even in extreme OOM situations. */ -#define MAX_UDP_CHUNK 1460 #define MAX_SKBS 32 #define USEC_PER_POLL 50 -#define MAX_SKB_SIZE \ - (sizeof(struct ethhdr) + \ - sizeof(struct iphdr) + \ - sizeof(struct udphdr) + \ - MAX_UDP_CHUNK) - static unsigned int carrier_timeout = 4; module_param(carrier_timeout, uint, 0644); -- 2.51.0