From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
Date: Mon, 18 Nov 2019 11:52:41 +0100
Subject: [PATCH FIX] brcmfmac: disable PCIe interrupts before bus reset
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Keeping interrupts on could result in brcmfmac freeing some resources
and then IRQ handlers trying to use them. That was obviously a straight
path for crashing a kernel.

Example:
CPU0                           CPU1
----                           ----
brcmf_pcie_reset
  brcmf_pcie_bus_console_read
  brcmf_detach
    ...
    brcmf_fweh_detach
    brcmf_proto_detach
                               brcmf_pcie_isr_thread
                                 ...
                                 brcmf_proto_msgbuf_rx_trigger
                                   ...
                                   drvr->proto->pd
    brcmf_pcie_release_irq

[  363.789218] Unable to handle kernel NULL pointer dereference at virtual address 00000038
[  363.797339] pgd = c0004000
[  363.800050] [00000038] *pgd=00000000
[  363.803635] Internal error: Oops: 17 [#1] SMP ARM
(...)
[  364.029209] Backtrace:
[  364.031725] [<bf243838>] (brcmf_proto_msgbuf_rx_trigger [brcmfmac]) from [<bf2471dc>] (brcmf_pcie_isr_thread+0x228/0x274 [brcmfmac])
[  364.043662]  r7:00000001 r6:c8ca0000 r5:00010000 r4:c7b4f800

Fixes: 4684997d9eea ("brcmfmac: reset PCIe bus on a firmware crash")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
@@ -1437,6 +1437,8 @@ static int brcmf_pcie_reset(struct devic
 	struct brcmf_fw_request *fwreq;
 	int err;
 
+	brcmf_pcie_intr_disable(devinfo);
+
 	brcmf_pcie_bus_console_read(devinfo, true);
 
 	brcmf_detach(dev);
