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[2001:678:a5c:1202:7b92:9ac1:b9ef:5287]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-3a1fd13a484sm393461fa.38.2026.08.25.11.27.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Aug 2026 11:27:16 -0700 (PDT) Date: Tue, 25 Aug 2026 20:27:15 +0200 From: Klara Modin To: Devin Wittmayer Cc: Felix Fietkau , Lorenzo Bianconi , Charlie-cy Wu , JB Tsai , Sean Wang , Ryder Lee , Shayne Chen , Matthias Brugger , AngeloGioacchino Del Regno , linux-wireless@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, regressions@lists.linux.dev Subject: Re: [PATCH wireless] wifi: mt76: mt792x: fix NULL dereference in ACPI SAR init during probe Message-ID: References: <20260825181712.28548-1-lucid_duck@justthetip.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260825181712.28548-1-lucid_duck@justthetip.ca> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260825_112719_413543_BE622224 X-CRM114-Status: GOOD ( 29.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2026-08-25 11:17:12 -0700, Devin Wittmayer wrote: > Some laptops carry a MediaTek power table in their firmware, and the > driver reads it to set a transmit limit for each frequency range. It > only fills in the ranges themselves when it registers the device. > > The startup step that does this existed already, but it never programmed > anything. These two commits made it run a regulatory update instead, > which sets the limits on the way through, long before registration. So on > a machine that has the table the driver reads through an empty pointer > and the interface never appears: > > BUG: kernel NULL pointer dereference, address: 0000000000000004 > RIP: 0010:mt792x_init_acpi_sar_power > Call Trace: > mt7921_set_tx_sar_pwr > mt7921_mcu_regd_update > mt7921_regd_update > mt7921_run_firmware > mt7921e_mcu_init > mt7921_init_work > > Skip it when the ranges are missing. They are applied again once the > device is up, which is where they came from before. > > Reported-by: Klara Modin > Closes: https://lore.kernel.org/linux-wireless/aoyxqHYvSuaBeubf@soda.int.kasm.eu/ > Fixes: 9b80bd9cab40 ("wifi: mt76: mt7921: add regulatory wiphy self manager support") > Fixes: e9f3f1cc133f ("wifi: mt76: mt7925: add regulatory wiphy self manager support") > Signed-off-by: Devin Wittmayer > --- > > Reproduced on both chips before sending, an MT7922 and an MT7925, and the > fix clears both. Neither machine here ships a vendor power table, so I > supplied one through an ACPI override in the initrd. It also wants recent > firmware. The June builds do not turn on self-managed regulatory and > nothing happens; the builds now in linux-firmware do, and then it dies > exactly as reported with no interface at all. Patched, both come up and > scan normally, and the injected limits still show through in the power > table afterwards, so the skip does not lose them. > > With that table still in place and the fix absent, backing out the mt7921 > commit on its own also boots clean, so the table is not what causes this. > Thanks for the quick fix! Regards, Tested-by: Klara Modin > drivers/net/wireless/mediatek/mt76/mt792x_acpi_sar.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/wireless/mediatek/mt76/mt792x_acpi_sar.c b/drivers/net/wireless/mediatek/mt76/mt792x_acpi_sar.c > index 946dd7956e4a..b468051fbe68 100644 > --- a/drivers/net/wireless/mediatek/mt76/mt792x_acpi_sar.c > +++ b/drivers/net/wireless/mediatek/mt76/mt792x_acpi_sar.c > @@ -323,7 +323,8 @@ int mt792x_init_acpi_sar_power(struct mt792x_phy *phy, bool set_default) > const struct cfg80211_sar_capa *capa = phy->mt76->hw->wiphy->sar_capa; > int i; > > - if (!phy->acpisar || !((struct mt792x_acpi_sar *)phy->acpisar)->dyn) > + if (!capa || !phy->acpisar || > + !((struct mt792x_acpi_sar *)phy->acpisar)->dyn) > return 0; > > /* When ACPI SAR enabled in HW, we should apply rules for .frp > -- > 2.55.0 >