{"id":"CVE-2025-38017","state":"PUBLISHED","title":"fs/eventpoll: fix endless busy loop after timeout has expired","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/eventpoll: fix endless busy loop after timeout has expired\n\nAfter commit 0a65bc27bd64 (\"eventpoll: Set epoll timeout if it's in\nthe future\"), the following program would immediately enter a busy\nloop in the kernel:\n\n```\nint main() {\n  int e = epoll_create1(0);\n  struct epoll_event event = {.events = EPOLLIN};\n  epoll_ctl(e, EPOLL_CTL_ADD, 0, &event);\n  const struct timespec timeout = {.tv_nsec = 1};\n  epoll_pwait2(e, &event, 1, &timeout, 0);\n}\n```\n\nThis happens because the given (non-zero) timeout of 1 nanosecond\nusually expires before ep_poll() is entered and then\nep_schedule_timeout() returns false, but `timed_out` is never set\nbecause the code line that sets it is skipped.  This quickly turns\ninto a soft lockup, RCU stalls and deadlocks, inflicting severe\nheadaches to the whole system.\n\nWhen the timeout has expired, we don't need to schedule a hrtimer, but\nwe should set the `timed_out` variable.  Therefore, I suggest moving\nthe ep_schedule_timeout() check into the `timed_out` expression\ninstead of skipping it.\n\nbrauner: Note that there was an earlier fix by Joe Damato in response to\nmy bug report in [1].","publishedAt":"2025-06-18T09:28:25.790Z","updatedAt":"2026-05-11T21:19:42.321Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"99a0ad16dfd114a429df665065dcc576dad743c0","status":"affected","lessThan":"7631dca012593c95d36199082546a24a0058fc50","versionType":"git"},{"version":"0a65bc27bd645894175c059397b4916e31955fb2","status":"affected","lessThan":"d9ec73301099ec5975505e1c3effbe768bab9490","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/eventpoll.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6.14.4","status":"affected","lessThan":"6.14.8","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/eventpoll.c"]}],"references":["https://git.kernel.org/stable/c/7631dca012593c95d36199082546a24a0058fc50","https://git.kernel.org/stable/c/d9ec73301099ec5975505e1c3effbe768bab9490"],"weaknesses":[],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/38xxx/CVE-2025-38017.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-38017","state":"PUBLISHED","datePublished":"2025-06-18T09:28:25.790Z","dateUpdated":"2026-05-11T21:19:42.321Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T04:51:23.977Z"},"containers":{"cna":{"title":"fs/eventpoll: fix endless busy loop after timeout has expired","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/eventpoll: fix endless busy loop after timeout has expired\n\nAfter commit 0a65bc27bd64 (\"eventpoll: Set epoll timeout if it's in\nthe future\"), the following program would immediately enter a busy\nloop in the kernel:\n\n```\nint main() {\n  int e = epoll_create1(0);\n  struct epoll_event event = {.events = EPOLLIN};\n  epoll_ctl(e, EPOLL_CTL_ADD, 0, &event);\n  const struct timespec timeout = {.tv_nsec = 1};\n  epoll_pwait2(e, &event, 1, &timeout, 0);\n}\n```\n\nThis happens because the given (non-zero) timeout of 1 nanosecond\nusually expires before ep_poll() is entered and then\nep_schedule_timeout() returns false, but `timed_out` is never set\nbecause the code line that sets it is skipped.  This quickly turns\ninto a soft lockup, RCU stalls and deadlocks, inflicting severe\nheadaches to the whole system.\n\nWhen the timeout has expired, we don't need to schedule a hrtimer, but\nwe should set the `timed_out` variable.  Therefore, I suggest moving\nthe ep_schedule_timeout() check into the `timed_out` expression\ninstead of skipping it.\n\nbrauner: Note that there was an earlier fix by Joe Damato in response to\nmy bug report in [1]."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"99a0ad16dfd114a429df665065dcc576dad743c0","status":"affected","lessThan":"7631dca012593c95d36199082546a24a0058fc50","versionType":"git"},{"version":"0a65bc27bd645894175c059397b4916e31955fb2","status":"affected","lessThan":"d9ec73301099ec5975505e1c3effbe768bab9490","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/eventpoll.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6.14.4","status":"affected","lessThan":"6.14.8","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/eventpoll.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/7631dca012593c95d36199082546a24a0058fc50"},{"url":"https://git.kernel.org/stable/c/d9ec73301099ec5975505e1c3effbe768bab9490"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T21:19:42.321Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14.4","versionEndExcluding":"6.14.8"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}