{"id":"CVE-2026-52946","revision":"d7353f3e4bfd41a699f85fd6793c71cc","records":[{"revision":"d7353f3e4bfd41a699f85fd6793c71cc","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-52946","aliases":[],"title":"fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling\n\nA SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in\nsend_sigio() and send_sigurg() when a process group receives a signal.\n\nWhen FASYNC is configured for a process group (PIDTYPE_PGID), both\nfunctions use read_lock(&tasklist_lock) to traverse the task list.\nHowever, they are frequently called from softirq context:\n- send_sigio() via input_inject_event -> kill_fasync\n- send_sigurg() via tcp_check_urg -> sk_send_sigurg (NET_RX_SOFTIRQ)\n\nThe deadlock is caused by the rwlock writer fairness mechanism:\n1. CPU 0 (process context) holds read_lock(&tasklist_lock) in do_wait().\n2. CPU 1 (process context) attempts write_lock(&tasklist_lock) in\n fork() or exit() and spins, which blocks all new readers.\n3. CPU 0 is interrupted by a softirq (e.g., TCP URG packet reception).\n4. The softirq calls send_sigurg() and attempts to acquire\n read_lock(&tasklist_lock), deadlocking because CPU 1 is waiting.\n\nSince PID hashing and do_each_pid_task() traversals are already\nRCU-protected, the read_lock on tasklist_lock is no longer strictly\nrequired for safe traversal. Fix this by replacing tasklist_lock with\nrcu_read_lock(), aligning the process group signaling path with the\nsingle-PID path. This also mitigates a potential remote denial of\nservice vector via TCP URG packets.\n\nLockdep splat:\n=====================================================\nWARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected\n[...]\nChain exists of:\n &dev->event_lock --> &f_owner->lock --> tasklist_lock\n\nPossible interrupt unsafe locking scenario:\n CPU0 CPU1\n ---- ----\n lock(tasklist_lock);\n local_irq_disable();\n lock(&dev->event_lock);\n lock(&f_owner->lock);\n \n lock(&dev->event_lock);\n\n*** DEADLOCK ***","state":0,"publishedAt":"2026-06-24T16:26:04.419+00:00","modifiedAt":"2026-10-19T19:47:09.047+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/fcntl.c\"\n ],\n \"versions\": [\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"54626335ea4174ab2d9a183b511d825f6765e47b\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"897d6a7247739fb1528f98c575df4f2e5de7f994\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"32dbd5ce4be3a3ed7e00f8af18795cc84fc50a33\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"b5fa9e32fb6718f70c986ee14dd5d01b4846f331\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"1bee417678f1135e35b25a37734db46aa94258d2\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"20a93e397abe850c49b6fa0e8cc827b5f634a8f5\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"bfcc8e8d8a495bb34cae9e620adfb75fb13a3954\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"36c1b57b2ecf3c61ac93f5f07bd29b6f21e226ed\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"00633c4683828acd5256fa8d5163f440d74bbe71\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/fcntl.c\"\n ],\n \"versions\": [\n {\n \"version\": \"2.6.12\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"2.6.12\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.259\",\n \"lessThanOrEqual\": \"5.10.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.210\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.176\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.143\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.94\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.36\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.0.13\",\n \"lessThanOrEqual\": \"7.0.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.1.1\",\n \"lessThanOrEqual\": \"7.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.2\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/54626335ea4174ab2d9a183b511d825f6765e47b","https://git.kernel.org/stable/c/897d6a7247739fb1528f98c575df4f2e5de7f994","https://git.kernel.org/stable/c/32dbd5ce4be3a3ed7e00f8af18795cc84fc50a33","https://git.kernel.org/stable/c/b5fa9e32fb6718f70c986ee14dd5d01b4846f331","https://git.kernel.org/stable/c/1bee417678f1135e35b25a37734db46aa94258d2","https://git.kernel.org/stable/c/20a93e397abe850c49b6fa0e8cc827b5f634a8f5","https://git.kernel.org/stable/c/bfcc8e8d8a495bb34cae9e620adfb75fb13a3954","https://git.kernel.org/stable/c/36c1b57b2ecf3c61ac93f5f07bd29b6f21e226ed","https://git.kernel.org/stable/c/00633c4683828acd5256fa8d5163f440d74bbe71"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-52946","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-52946","identifiers":["CVE-2026-52946"]},"retained":false,"historicalAffected":[]}],"coverage":[]}