{"id":"CVE-2026-93168","state":"PUBLISHED","title":"dmaengine: xilinx_dma: Fix CPU stall in xilinx_dma_poll_timeout","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ndmaengine: xilinx_dma: Fix CPU stall in xilinx_dma_poll_timeout\n\nCurrently when calling xilinx_dma_poll_timeout with delay_us=0 and a\ncondition that is never fulfilled, the CPU busy-waits for prolonged time\nand the timeout triggers only with a massive delay causing a CPU stall.\n\nThis happens due to a huge underestimation of wall clock time in\npoll_timeout_us_atomic. Commit 7349a69cf312 (\"iopoll: Do not use\ntimekeeping in read_poll_timeout_atomic()\") changed the behavior to no\nlonger use ktime_get at the expense of underestimation of wall clock\ntime which appears to be very large for delay_us=0. Instead of timing\nout after approximately XILINX_DMA_LOOP_COUNT microseconds, the timeout\ntakes XILINX_DMA_LOOP_COUNT * 1000 * (time that the overhead of the for\nloop in poll_timeout_us_atomic takes) which is in the range of several\nminutes for XILINX_DMA_LOOP_COUNT=1000000. Fix this by using a non-zero\nvalue for delay_us. Use delay_us=10 to keep the delay in the hot path of\nstarting DMA transfers minimal but still avoid CPU stalls in case of\nunexpected hardware failures.\n\nOne-off measurement with delay_us=0 causes the cpu to busy wait around 7\nminutes in the timeout case. After applying this patch with delay_us=10\nthe measured timeout was 1053428 microseconds which is roughly\nequivalent to the expected 1000000 microseconds specified in\nXILINX_DMA_LOOP_COUNT.\n\nAdd a constant XILINX_DMA_POLL_DELAY_US for delay_us value.","publishedAt":"2026-09-17T16:11:59.904Z","updatedAt":"2026-10-30T12:36:12.039Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"4237b5cc181a17f5a2a797655c1ce2c64e01c550","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"2ba67aa183a3ce174d534425b67eda84f6e3c896","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"c30a26d4987a01e619449bf170f584c007e07d75","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"f786e7b3adbf3bd14964a1cedf9d55b6ad91dcd7","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"8b5654d317277e6e505c23f8fa7e415237fefc7f","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"aa99c4d1d63bbc26a5fc4c667d89b2595743c19d","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/dma/xilinx/xilinx_dma.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.6","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/dma/xilinx/xilinx_dma.c"]}],"references":["https://git.kernel.org/stable/c/4237b5cc181a17f5a2a797655c1ce2c64e01c550","https://git.kernel.org/stable/c/2ba67aa183a3ce174d534425b67eda84f6e3c896","https://git.kernel.org/stable/c/c30a26d4987a01e619449bf170f584c007e07d75","https://git.kernel.org/stable/c/f786e7b3adbf3bd14964a1cedf9d55b6ad91dcd7","https://git.kernel.org/stable/c/8b5654d317277e6e505c23f8fa7e415237fefc7f","https://git.kernel.org/stable/c/aa99c4d1d63bbc26a5fc4c667d89b2595743c19d"],"weaknesses":[],"ingestedAt":"2026-10-30T12:56:04.490Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/93xxx/CVE-2026-93168.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-93168","state":"PUBLISHED","datePublished":"2026-09-17T16:11:59.904Z","dateUpdated":"2026-10-30T12:36:12.039Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-17T16:02:15.090Z"},"containers":{"cna":{"title":"dmaengine: xilinx_dma: Fix CPU stall in xilinx_dma_poll_timeout","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ndmaengine: xilinx_dma: Fix CPU stall in xilinx_dma_poll_timeout\n\nCurrently when calling xilinx_dma_poll_timeout with delay_us=0 and a\ncondition that is never fulfilled, the CPU busy-waits for prolonged time\nand the timeout triggers only with a massive delay causing a CPU stall.\n\nThis happens due to a huge underestimation of wall clock time in\npoll_timeout_us_atomic. Commit 7349a69cf312 (\"iopoll: Do not use\ntimekeeping in read_poll_timeout_atomic()\") changed the behavior to no\nlonger use ktime_get at the expense of underestimation of wall clock\ntime which appears to be very large for delay_us=0. Instead of timing\nout after approximately XILINX_DMA_LOOP_COUNT microseconds, the timeout\ntakes XILINX_DMA_LOOP_COUNT * 1000 * (time that the overhead of the for\nloop in poll_timeout_us_atomic takes) which is in the range of several\nminutes for XILINX_DMA_LOOP_COUNT=1000000. Fix this by using a non-zero\nvalue for delay_us. Use delay_us=10 to keep the delay in the hot path of\nstarting DMA transfers minimal but still avoid CPU stalls in case of\nunexpected hardware failures.\n\nOne-off measurement with delay_us=0 causes the cpu to busy wait around 7\nminutes in the timeout case. After applying this patch with delay_us=10\nthe measured timeout was 1053428 microseconds which is roughly\nequivalent to the expected 1000000 microseconds specified in\nXILINX_DMA_LOOP_COUNT.\n\nAdd a constant XILINX_DMA_POLL_DELAY_US for delay_us value."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"4237b5cc181a17f5a2a797655c1ce2c64e01c550","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"2ba67aa183a3ce174d534425b67eda84f6e3c896","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"c30a26d4987a01e619449bf170f584c007e07d75","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"f786e7b3adbf3bd14964a1cedf9d55b6ad91dcd7","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"8b5654d317277e6e505c23f8fa7e415237fefc7f","versionType":"git"},{"version":"9495f2648287029fb5545c34a0fa318426ebe84c","status":"affected","lessThan":"aa99c4d1d63bbc26a5fc4c667d89b2595743c19d","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/dma/xilinx/xilinx_dma.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.6","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/dma/xilinx/xilinx_dma.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/4237b5cc181a17f5a2a797655c1ce2c64e01c550"},{"url":"https://git.kernel.org/stable/c/2ba67aa183a3ce174d534425b67eda84f6e3c896"},{"url":"https://git.kernel.org/stable/c/c30a26d4987a01e619449bf170f584c007e07d75"},{"url":"https://git.kernel.org/stable/c/f786e7b3adbf3bd14964a1cedf9d55b6ad91dcd7"},{"url":"https://git.kernel.org/stable/c/8b5654d317277e6e505c23f8fa7e415237fefc7f"},{"url":"https://git.kernel.org/stable/c/aa99c4d1d63bbc26a5fc4c667d89b2595743c19d"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:36:12.039Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.6","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}