CVE-2026-93168 is a vulnerability in Linux Kernel
Published on September 17, 2026
dmaengine: xilinx_dma: Fix CPU stall in xilinx_dma_poll_timeout
In the Linux kernel, the following vulnerability has been resolved:
dmaengine: xilinx_dma: Fix CPU stall in xilinx_dma_poll_timeout
Currently when calling xilinx_dma_poll_timeout with delay_us=0 and a
condition that is never fulfilled, the CPU busy-waits for prolonged time
and the timeout triggers only with a massive delay causing a CPU stall.
This happens due to a huge underestimation of wall clock time in
poll_timeout_us_atomic. Commit 7349a69cf312 ("iopoll: Do not use
timekeeping in read_poll_timeout_atomic()") changed the behavior to no
longer use ktime_get at the expense of underestimation of wall clock
time which appears to be very large for delay_us=0. Instead of timing
out after approximately XILINX_DMA_LOOP_COUNT microseconds, the timeout
takes XILINX_DMA_LOOP_COUNT * 1000 * (time that the overhead of the for
loop in poll_timeout_us_atomic takes) which is in the range of several
minutes for XILINX_DMA_LOOP_COUNT=1000000. Fix this by using a non-zero
value for delay_us. Use delay_us=10 to keep the delay in the hot path of
starting DMA transfers minimal but still avoid CPU stalls in case of
unexpected hardware failures.
One-off measurement with delay_us=0 causes the cpu to busy wait around 7
minutes in the timeout case. After applying this patch with delay_us=10
the measured timeout was 1053428 microseconds which is roughly
equivalent to the expected 1000000 microseconds specified in
XILINX_DMA_LOOP_COUNT.
Add a constant XILINX_DMA_POLL_DELAY_US for delay_us value.
Products Associated with CVE-2026-93168
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Affected Versions
Linux:- Version 9495f2648287029fb5545c34a0fa318426ebe84c and below 8b5654d317277e6e505c23f8fa7e415237fefc7f is affected.
- Version 9495f2648287029fb5545c34a0fa318426ebe84c and below aa99c4d1d63bbc26a5fc4c667d89b2595743c19d is affected.
- Version 4.6 is affected.
- Before 4.6 is unaffected.
- Version 7.2.6, <= 7.2.* is unaffected.
- Version 7.3-rc1, <= * is unaffected.