[PATCH 0/4] wcn36xx: Fix DMA buffer allocation and free logic
Bryan O'Donoghue
bryan.odonoghue at linaro.org
Fri Oct 15 06:17:37 PDT 2021
Digging around through some bugs reported from an extensive testing cycle
we've found that wcn36xx has a number of unexplained RX related oopses.
In at least one case we appear to have DMA'd data to an unmapped region.
The written data appears to be a correctly formed DMA buffer descriptor - a
DXE BD in WCNSS parlance, with an AP beacon inside of it.
Reasoning about how such a situation might come about and reviewing the
run-time code, there was no obvious path where we might free a BD or an
skbuff pointed to by a BD, which DXE might not be aware of.
However looking at the ieee80211_ops.start and ieee80211_ops.stop callbacks
in wcn36xx we can see a number of bugs associated with BD allocation, error
handling and leaving the DMA engine active, despite freeing SKBs on the MSM
side.
This last mention - failure to quiesce potential DMA from the downstream
agent - WCNSS DXE despite freeing the memory @ the skbuffs is a decent
candidate for our unexplained upstream DMA transaction to unmapped memory.
Since wcn36xx_stop and wcn36xx_start can be called a number of times by the
controlling upper layers it means there is a potential gap between
wcn36xx_stop and wcn36xx_start which could leave WCNSS in a state where it
will try to DMA to memory we have freed.
This series addresses the obvious bugs that jump out on the start()/stop()
path.
Patch #1
In order to make it easier to read the DXE code, I've moved all of the
lock taking and freeing for DXE into dxe.c
Patch #2
Fixes a very obviously broken channel enable/disable cycle
Patch #3
Fixes a very obvious memory leak with dma_alloc_coherent()
Patch #4
Makes sure before we release skbuffs which we assigned to the RX channels
that we ensure the DXE block is put into reset
Bryan O'Donoghue (4):
wcn36xx: Fix DXE lock layering violation
wcn36xx: Fix DXE/DMA channel enable/disable cycle
wcn36xx: Release DMA channel descriptor allocations
wcn36xx: Put DXE block into reset before freeing memory
drivers/net/wireless/ath/wcn36xx/dxe.c | 75 +++++++++++++++++++++----
drivers/net/wireless/ath/wcn36xx/dxe.h | 2 +
drivers/net/wireless/ath/wcn36xx/txrx.c | 15 +----
3 files changed, 68 insertions(+), 24 deletions(-)
--
2.33.0
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