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([2a0d:3344:5521:6b10:2eb7:f61a:75:4534]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493be81df2asm159515325e9.12.2026.07.01.08.06.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Jul 2026 08:06:57 -0700 (PDT) Message-ID: Date: Wed, 1 Jul 2026 17:06:56 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] net: fman: guard IRQ handlers against pre-init interrupt To: ZhaoJinming , horms@kernel.org, andrew@lunn.ch, madalin.bucur@nxp.com Cc: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, sean.anderson@linux.dev References: <20260629084529.3709393-1-zhaojinming@uniontech.com> From: Paolo Abeni Content-Language: en-US In-Reply-To: <20260629084529.3709393-1-zhaojinming@uniontech.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/29/26 10:45 AM, ZhaoJinming wrote: > read_dts_node() registers shared interrupt handlers via > devm_request_irq() with fman as the dev_id, passing it to fman_irq() > and fman_err_irq(). At registration time, fman is only partially > initialized -- kzalloc_obj() zero-initializes all fields, so > fman->cfg and fman->fpm_regs are NULL. > > The handlers guard against incomplete initialization via: > > if (!is_init_done(fman->cfg)) > return IRQ_NONE; > > However, is_init_done(NULL) returns true (intended to indicate that > fman_init() has completed and cfg has been freed). This means when > cfg is NULL before fman_config() allocates it, the guard does not > take effect: > > is_init_done(NULL) -> returns true > !true -> false > guard skipped -> proceeds to dereference NULL fpm_regs > > If another device on the same shared IRQ line fires during the window > between devm_request_irq() and fman_init(), the handler accesses > NULL fman->fpm_regs via ioread32be(), causing a crash. The window > includes of_platform_populate() which can be slow. > > Add an irq_ready flag to struct fman that is set to true only after > fman_init() completes in fman_probe(). Check this flag at the start > of fman_irq() and fman_err_irq() before any register access. > > Use READ_ONCE()/WRITE_ONCE() for the flag accesses since it is a > cross-context shared variable written in process context and read > in interrupt context. > > This issue was identified in code review during the discussion of a > separate IRQF_SHARED UAF fix patch: > https://lore.kernel.org/netdev/20260626162323.GE1310988@horms.kernel.org/ > > Signed-off-by: ZhaoJinming > --- > drivers/net/ethernet/freescale/fman/fman.c | 5 +++++ > drivers/net/ethernet/freescale/fman/fman.h | 1 + > 2 files changed, 6 insertions(+) > > diff --git a/drivers/net/ethernet/freescale/fman/fman.c b/drivers/net/ethernet/freescale/fman/fman.c > index 013273a2de32..f14cb02d85a4 100644 > --- a/drivers/net/ethernet/freescale/fman/fman.c > +++ b/drivers/net/ethernet/freescale/fman/fman.c > @@ -2510,6 +2510,8 @@ static irqreturn_t fman_err_irq(int irq, void *handle) > struct fman_fpm_regs __iomem *fpm_rg; > irqreturn_t single_ret, ret = IRQ_NONE; > > + if (!READ_ONCE(fman->irq_ready)) > + return IRQ_NONE; Sashiko noted that on weakly ordered arch this could not be enough: https://sashiko.dev/#/patchset/20260629084529.3709393-1-zhaojinming%40uniontech.com Also I have the feeling this is papering over the real issue. Why initializing the irq when the driver is not yet ready? Why don't move IRQ initialization later? /P