CVE-2022-48898

In the Linux kernel, the following vulnerability has been resolved:

drm/msm/dp: do not complete dpauxcmdfifotx() if irq is not for aux transfer

There are 3 possible interrupt sources are handled by DP controller, HPDstatus, Controller state changes and Aux read/write transaction. At every irq, DP controller have to check isr status of every interrupt sources and service the interrupt if its isr status bits shows interrupts are pending. There is potential race condition may happen at current aux isr handler implementation since it is always complete dpauxcmdfifotx() even irq is not for aux read or write transaction. This may cause aux read transaction return premature if host aux data read is in the middle of waiting for sink to complete transferring data to host while irq happen. This will cause host's receiving buffer contains unexpected data. This patch fixes this problem by checking aux isr and return immediately at aux isr handler if there are no any isr status bits set.

Current there is a bug report regrading eDP edid corruption happen during system booting up. After lengthy debugging to found that VIDEOREADY interrupt was continuously firing during system booting up which cause dpauxisr() to complete dpauxcmdfifo_tx() prematurely to retrieve data from aux hardware buffer which is not yet contains complete data transfer from sink. This cause edid corruption.

Follows are the signature at kernel logs when problem happen, EDID has corrupt header panel-simple-dp-aux aux-aea0000.edp: Couldn't identify panel via EDID

Changes in v2: -- do complete if (ret == IRQHANDLED) ay dp-auxisr() -- add more commit text

Changes in v3: -- add Stephen suggested -- dpauxisr() return IRQXXX back to caller -- dpctrlisr() return IRQXXX back to caller

Changes in v4: -- split into two patches

Changes in v5: -- delete empty line between tags

Changes in v6: -- remove extra "that" and fixed line more than 75 char at commit text

Patchwork: https://patchwork.freedesktop.org/patch/516121/