Re: [PATCH] mwifiex: fix kernel crash after shutdown command timeout
From: Brian Norris <briannorris@chromium.org>
Date: 2017-03-14 18:33:13
Hi Amit, You managed to CC several other Google folks, but not me, the one who actually reviewed most of this! You might consider including me in the future :) On Fri, Feb 24, 2017 at 06:59:24PM +0530, Amitkumar Karwar wrote:
We observed a SHUTDOWN command timeout during reboot stress test due to a corner case firmware bug. It leads to use-after-free on adapter structure pointer and crash. We already have a cancel_work_sync() call in teardown thread. This issue is fixed by having this call just before mwifiex_remove_card(). At this point no further work will be scheduled. Signed-off-by: Amitkumar Karwar <redacted> Signed-off-by: Cathy Luo <redacted>
I'm testing this artificially by testing things like this concurrently: rmmod mwifiex_pcie & cat /sys/kernel/debug/mwifiex/mlan0/device_dump I'm using a 4.4-based kernel (plus quite a few backports) at the moment and I'm having problems (I can retest on upstream if really needed), and pretty sure this patch is buggy.
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--- drivers/net/wireless/marvell/mwifiex/pcie.c | 3 +-- drivers/net/wireless/marvell/mwifiex/sdio.c | 3 +-- 2 files changed, 2 insertions(+), 4 deletions(-)diff --git a/drivers/net/wireless/marvell/mwifiex/pcie.c b/drivers/net/wireless/marvell/mwifiex/pcie.c index a0d9180..f31c5ea 100644 --- a/drivers/net/wireless/marvell/mwifiex/pcie.c +++ b/drivers/net/wireless/marvell/mwifiex/pcie.c@@ -294,8 +294,6 @@ static void mwifiex_pcie_remove(struct pci_dev *pdev) if (!adapter || !adapter->priv_num) return; - cancel_work_sync(&card->work); - reg = card->pcie.reg; if (reg) ret = mwifiex_read_reg(adapter, reg->fw_status, &fw_status);@@ -312,6 +310,7 @@ static void mwifiex_pcie_remove(struct pci_dev *pdev) mwifiex_init_shutdown_fw(priv, MWIFIEX_FUNC_SHUTDOWN); } + cancel_work_sync(&card->work);
I don't think we want to move the cancellation to be this far; see the mwifiex_init_shutdown_fw() above! If I add a msleep(3000) below this, then run: rmmod mwifiex_pcie & sleep 0.5; cat /sys/kernel/debug/mwifiex/mlan0/device_dump I can trigger an abort in mwifiex_pcie_rdwr_firmware(). The problem is that you still allow a command timeout + firmware dump worker to still race with the shutdown -- in this case, I think it's mwifiex_init_shutdown_fw() that's disabling the device. I think the real solution is to, somewhere before we shutdown the firmware, *really* prevent any further work to be scheduled to &card->work. Maybe that means adding another flag so that the worker will just abort quickly in that case? So it's something like: card->worker_flags |= DONT_RUN_ANY_MORE; cancel_work_sync(&card->work); ... (this can be done either above the FIRMWARE_READY_PCIE check, or else you need to write a different version for FIRMWARE_READY_PCIE vs. !FIRMWARE_READY_PCIE) ... but definitely before mwifiex_init_shutdown_fw() ) ... And in mwifiex_pcie_work(): if (card->worker_flags & DONT_RUN_ANY_MORE) return; IOW, NAK to this patch. Brian
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mwifiex_remove_card(adapter); }diff --git a/drivers/net/wireless/marvell/mwifiex/sdio.c b/drivers/net/wireless/marvell/mwifiex/sdio.c index a4b356d..9534b47 100644 --- a/drivers/net/wireless/marvell/mwifiex/sdio.c +++ b/drivers/net/wireless/marvell/mwifiex/sdio.c@@ -387,8 +387,6 @@ static int mwifiex_check_winner_status(struct mwifiex_adapter *adapter) if (!adapter || !adapter->priv_num) return; - cancel_work_sync(&card->work); - mwifiex_dbg(adapter, INFO, "info: SDIO func num=%d\n", func->num); ret = mwifiex_sdio_read_fw_status(adapter, &firmware_stat);@@ -400,6 +398,7 @@ static int mwifiex_check_winner_status(struct mwifiex_adapter *adapter) mwifiex_init_shutdown_fw(priv, MWIFIEX_FUNC_SHUTDOWN); } + cancel_work_sync(&card->work); mwifiex_remove_card(adapter); }-- 1.9.1