dmaengine: xilinx_dma: Fix CPU stall in xilinx_dma_poll_timeout

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-93168
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-17 17:18:12 UTC
Updated2026-09-17 17:18:12 UTC
DescriptionIn 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.

Risk And Classification

EPSS: 0.001550000 probability, percentile 0.051260000 (date 2026-09-19)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 9495f2648287029fb5545c34a0fa318426ebe84c 8b5654d317277e6e505c23f8fa7e415237fefc7f git Not specified
CNA Linux Linux affected 9495f2648287029fb5545c34a0fa318426ebe84c aa99c4d1d63bbc26a5fc4c667d89b2595743c19d git Not specified
CNA Linux Linux affected 4.6 Not specified
CNA Linux Linux unaffected 4.6 semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/8b5654d317277e6e505c23f8fa7e415237fefc7f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/aa99c4d1d63bbc26a5fc4c667d89b2595743c19d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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