From: Andrew Lunn <andrew@lunn.ch>
To: Kriish Sharma <kriish.sharma2006@gmail.com>
Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, horms@kernel.org, willemb@google.com,
kerneljasonxing@gmail.com, martin.lau@kernel.org, mhal@rbox.co,
almasrymina@google.com, ebiggers@google.com,
aleksander.lobakin@intel.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, skhan@linuxfoundation.org,
syzbot+5a2250fd91b28106c37b@syzkaller.appspotmail.com
Subject: Re: [PATCH] net: skb: guard kmalloc_reserve() against oversized allocations
Date: Sat, 20 Sep 2025 17:38:37 +0200 [thread overview]
Message-ID: <34a4e8db-b0b8-4ad8-b8a2-bdfd69cc8b00@lunn.ch> (raw)
In-Reply-To: <20250920113723.380498-1-kriish.sharma2006@gmail.com>
On Sat, Sep 20, 2025 at 11:37:23AM +0000, Kriish Sharma wrote:
> Add an explicit size check in kmalloc_reserve() to reject requests
> larger than KMALLOC_MAX_SIZE before they reach the allocator.
>
> syzbot reported warnings triggered by attempts to allocate buffers
> with an object size exceeding KMALLOC_MAX_SIZE. While the existing
> code relies on kmalloc() failure and a comment states that truncation
> is "harmless", in practice this causes high-order allocation warnings
> and noisy kernel logs that interfere with testing.
>
> This patch introduces an early guard in kmalloc_reserve() that returns
> NULL if obj_size exceeds KMALLOC_MAX_SIZE. This ensures impossible
> requests fail fast and silently, avoiding allocator warnings while
> keeping the intended semantics unchanged.
What is the value of KMALLOC_MAX_SIZE? Do we actually want a
warn_once() here because it indicates a driver bug, or missing
validation of user space parameters?
Andrew
prev parent reply other threads:[~2025-09-20 15:38 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-20 11:37 Kriish Sharma
2025-09-20 15:38 ` Andrew Lunn [this message]
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