{"dataType": "CVE_RECORD", "dataVersion": "5.1", "cveMetadata": {"cveId": "CVE-2021-47069", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-02-29T22:33:44.296Z", "datePublished": "2024-03-01T21:15:08.598Z", "dateUpdated": "2024-12-19T07:34:40.475Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2024-12-19T07:34:40.475Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry\n\ndo_mq_timedreceive calls wq_sleep with a stack local address. The\nsender (do_mq_timedsend) uses this address to later call pipelined_send.\n\nThis leads to a very hard to trigger race where a do_mq_timedreceive\ncall might return and leave do_mq_timedsend to rely on an invalid\naddress, causing the following crash:\n\n RIP: 0010:wake_q_add_safe+0x13/0x60\n Call Trace:\n __x64_sys_mq_timedsend+0x2a9/0x490\n do_syscall_64+0x80/0x680\n entry_SYSCALL_64_after_hwframe+0x44/0xa9\n RIP: 0033:0x7f5928e40343\n\nThe race occurs as:\n\n1. do_mq_timedreceive calls wq_sleep with the address of `struct\n ext_wait_queue` on function stack (aliased as `ewq_addr` here) - it\n holds a valid `struct ext_wait_queue *` as long as the stack has not\n been overwritten.\n\n2. `ewq_addr` gets added to info->e_wait_q[RECV].list in wq_add, and\n do_mq_timedsend receives it via wq_get_first_waiter(info, RECV) to call\n __pipelined_op.\n\n3. Sender calls __pipelined_op::smp_store_release(&this->state,\n STATE_READY). Here is where the race window begins. (`this` is\n `ewq_addr`.)\n\n4. If the receiver wakes up now in do_mq_timedreceive::wq_sleep, it\n will see `state == STATE_READY` and break.\n\n5. do_mq_timedreceive returns, and `ewq_addr` is no longer guaranteed\n to be a `struct ext_wait_queue *` since it was on do_mq_timedreceive's\n stack. (Although the address may not get overwritten until another\n function happens to touch it, which means it can persist around for an\n indefinite time.)\n\n6. do_mq_timedsend::__pipelined_op() still believes `ewq_addr` is a\n `struct ext_wait_queue *`, and uses it to find a task_struct to pass to\n the wake_q_add_safe call. In the lucky case where nothing has\n overwritten `ewq_addr` yet, `ewq_addr->task` is the right task_struct.\n In the unlucky case, __pipelined_op::wake_q_add_safe gets handed a\n bogus address as the receiver's task_struct causing the crash.\n\ndo_mq_timedsend::__pipelined_op() should not dereference `this` after\nsetting STATE_READY, as the receiver counterpart is now free to return.\nChange __pipelined_op to call wake_q_add_safe on the receiver's\ntask_struct returned by get_task_struct, instead of dereferencing `this`\nwhich sits on the receiver's stack.\n\nAs Manfred pointed out, the race potentially also exists in\nipc/msg.c::expunge_all and ipc/sem.c::wake_up_sem_queue_prepare. Fix\nthose in the same way."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["ipc/mqueue.c", "ipc/msg.c", "ipc/sem.c"], "versions": [{"version": "0d97a82ba830d89a1e541cc9cd11f1e38c28e416", "lessThan": "4528c0c323085e645b8765913b4a7fd42cf49b65", "status": "affected", "versionType": "git"}, {"version": "0d97a82ba830d89a1e541cc9cd11f1e38c28e416", "lessThan": "807fa14536b26803b858da878b643be72952a097", "status": "affected", "versionType": "git"}, {"version": "0d97a82ba830d89a1e541cc9cd11f1e38c28e416", "lessThan": "a11ddb37bf367e6b5239b95ca759e5389bb46048", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["ipc/mqueue.c", "ipc/msg.c", "ipc/sem.c"], "versions": [{"version": "5.6", "status": "affected"}, {"version": "0", "lessThan": "5.6", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.40", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.12.7", "lessThanOrEqual": "5.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.13", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "references": [{"url": "https://git.kernel.org/stable/c/4528c0c323085e645b8765913b4a7fd42cf49b65"}, {"url": "https://git.kernel.org/stable/c/807fa14536b26803b858da878b643be72952a097"}, {"url": "https://git.kernel.org/stable/c/a11ddb37bf367e6b5239b95ca759e5389bb46048"}], "title": "ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry", "x_generator": {"engine": "bippy-5f407fcff5a0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2024-06-21T16:15:09.996738Z", "id": "CVE-2021-47069", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-06-21T16:15:20.262Z"}}, {"providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:24:39.653Z"}, "title": "CVE Program Container", "references": [{"url": "https://git.kernel.org/stable/c/4528c0c323085e645b8765913b4a7fd42cf49b65", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/807fa14536b26803b858da878b643be72952a097", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/a11ddb37bf367e6b5239b95ca759e5389bb46048", "tags": ["x_transferred"]}]}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CVE Program Container", "references": [{"url": "https://git.kernel.org/stable/c/4528c0c323085e645b8765913b4a7fd42cf49b65", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/807fa14536b26803b858da878b643be72952a097", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/a11ddb37bf367e6b5239b95ca759e5389bb46048", "tags": ["x_transferred"]}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:24:39.653Z"}}, {"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2021-47069", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2024-06-21T16:15:09.996738Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-06-21T16:15:15.682Z"}}], "cna": {"title": "ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry", "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "0d97a82ba830d89a1e541cc9cd11f1e38c28e416", "lessThan": "4528c0c323085e645b8765913b4a7fd42cf49b65", "versionType": "git"}, {"status": "affected", "version": "0d97a82ba830d89a1e541cc9cd11f1e38c28e416", "lessThan": "807fa14536b26803b858da878b643be72952a097", "versionType": "git"}, {"status": "affected", "version": "0d97a82ba830d89a1e541cc9cd11f1e38c28e416", "lessThan": "a11ddb37bf367e6b5239b95ca759e5389bb46048", "versionType": "git"}], "programFiles": ["ipc/mqueue.c", "ipc/msg.c", "ipc/sem.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "5.6"}, {"status": "unaffected", "version": "0", "lessThan": "5.6", "versionType": "semver"}, {"status": "unaffected", "version": "5.10.40", "versionType": "semver", "lessThanOrEqual": "5.10.*"}, {"status": "unaffected", "version": "5.12.7", "versionType": "semver", "lessThanOrEqual": "5.12.*"}, {"status": "unaffected", "version": "5.13", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["ipc/mqueue.c", "ipc/msg.c", "ipc/sem.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/4528c0c323085e645b8765913b4a7fd42cf49b65"}, {"url": "https://git.kernel.org/stable/c/807fa14536b26803b858da878b643be72952a097"}, {"url": "https://git.kernel.org/stable/c/a11ddb37bf367e6b5239b95ca759e5389bb46048"}], "x_generator": {"engine": "bippy-5f407fcff5a0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry\n\ndo_mq_timedreceive calls wq_sleep with a stack local address. The\nsender (do_mq_timedsend) uses this address to later call pipelined_send.\n\nThis leads to a very hard to trigger race where a do_mq_timedreceive\ncall might return and leave do_mq_timedsend to rely on an invalid\naddress, causing the following crash:\n\n RIP: 0010:wake_q_add_safe+0x13/0x60\n Call Trace:\n __x64_sys_mq_timedsend+0x2a9/0x490\n do_syscall_64+0x80/0x680\n entry_SYSCALL_64_after_hwframe+0x44/0xa9\n RIP: 0033:0x7f5928e40343\n\nThe race occurs as:\n\n1. do_mq_timedreceive calls wq_sleep with the address of `struct\n ext_wait_queue` on function stack (aliased as `ewq_addr` here) - it\n holds a valid `struct ext_wait_queue *` as long as the stack has not\n been overwritten.\n\n2. `ewq_addr` gets added to info->e_wait_q[RECV].list in wq_add, and\n do_mq_timedsend receives it via wq_get_first_waiter(info, RECV) to call\n __pipelined_op.\n\n3. Sender calls __pipelined_op::smp_store_release(&this->state,\n STATE_READY). Here is where the race window begins. (`this` is\n `ewq_addr`.)\n\n4. If the receiver wakes up now in do_mq_timedreceive::wq_sleep, it\n will see `state == STATE_READY` and break.\n\n5. do_mq_timedreceive returns, and `ewq_addr` is no longer guaranteed\n to be a `struct ext_wait_queue *` since it was on do_mq_timedreceive's\n stack. (Although the address may not get overwritten until another\n function happens to touch it, which means it can persist around for an\n indefinite time.)\n\n6. do_mq_timedsend::__pipelined_op() still believes `ewq_addr` is a\n `struct ext_wait_queue *`, and uses it to find a task_struct to pass to\n the wake_q_add_safe call. In the lucky case where nothing has\n overwritten `ewq_addr` yet, `ewq_addr->task` is the right task_struct.\n In the unlucky case, __pipelined_op::wake_q_add_safe gets handed a\n bogus address as the receiver's task_struct causing the crash.\n\ndo_mq_timedsend::__pipelined_op() should not dereference `this` after\nsetting STATE_READY, as the receiver counterpart is now free to return.\nChange __pipelined_op to call wake_q_add_safe on the receiver's\ntask_struct returned by get_task_struct, instead of dereferencing `this`\nwhich sits on the receiver's stack.\n\nAs Manfred pointed out, the race potentially also exists in\nipc/msg.c::expunge_all and ipc/sem.c::wake_up_sem_queue_prepare. Fix\nthose in the same way."}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2024-12-19T07:34:40.475Z"}}}, "cveMetadata": {"cveId": "CVE-2021-47069", "state": "PUBLISHED", "dateUpdated": "2024-12-19T07:34:40.475Z", "dateReserved": "2024-02-29T22:33:44.296Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2024-03-01T21:15:08.598Z", "assignerShortName": "Linux"}, "dataVersion": "5.1"}

{"descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry\n\ndo_mq_timedreceive calls wq_sleep with a stack local address. The\nsender (do_mq_timedsend) uses this address to later call pipelined_send.\n\nThis leads to a very hard to trigger race where a do_mq_timedreceive\ncall might return and leave do_mq_timedsend to rely on an invalid\naddress, causing the following crash:\n\n RIP: 0010:wake_q_add_safe+0x13/0x60\n Call Trace:\n __x64_sys_mq_timedsend+0x2a9/0x490\n do_syscall_64+0x80/0x680\n entry_SYSCALL_64_after_hwframe+0x44/0xa9\n RIP: 0033:0x7f5928e40343\n\nThe race occurs as:\n\n1. do_mq_timedreceive calls wq_sleep with the address of `struct\n ext_wait_queue` on function stack (aliased as `ewq_addr` here) - it\n holds a valid `struct ext_wait_queue *` as long as the stack has not\n been overwritten.\n\n2. `ewq_addr` gets added to info->e_wait_q[RECV].list in wq_add, and\n do_mq_timedsend receives it via wq_get_first_waiter(info, RECV) to call\n __pipelined_op.\n\n3. Sender calls __pipelined_op::smp_store_release(&this->state,\n STATE_READY). Here is where the race window begins. (`this` is\n `ewq_addr`.)\n\n4. If the receiver wakes up now in do_mq_timedreceive::wq_sleep, it\n will see `state == STATE_READY` and break.\n\n5. do_mq_timedreceive returns, and `ewq_addr` is no longer guaranteed\n to be a `struct ext_wait_queue *` since it was on do_mq_timedreceive's\n stack. (Although the address may not get overwritten until another\n function happens to touch it, which means it can persist around for an\n indefinite time.)\n\n6. do_mq_timedsend::__pipelined_op() still believes `ewq_addr` is a\n `struct ext_wait_queue *`, and uses it to find a task_struct to pass to\n the wake_q_add_safe call. In the lucky case where nothing has\n overwritten `ewq_addr` yet, `ewq_addr->task` is the right task_struct.\n In the unlucky case, __pipelined_op::wake_q_add_safe gets handed a\n bogus address as the receiver's task_struct causing the crash.\n\ndo_mq_timedsend::__pipelined_op() should not dereference `this` after\nsetting STATE_READY, as the receiver counterpart is now free to return.\nChange __pipelined_op to call wake_q_add_safe on the receiver's\ntask_struct returned by get_task_struct, instead of dereferencing `this`\nwhich sits on the receiver's stack.\n\nAs Manfred pointed out, the race potentially also exists in\nipc/msg.c::expunge_all and ipc/sem.c::wake_up_sem_queue_prepare. Fix\nthose in the same way."}, {"lang": "es", "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: ipc/mqueue, msg, sem: evite confiar en una referencia de pila despu\u00e9s de su vencimiento do_mq_timedreceive llama a wq_sleep con una direcci\u00f3n local de pila. El remitente (do_mq_timedsend) usa esta direcci\u00f3n para luego llamar a pipelined_send. Esto conduce a una ejecuci\u00f3n muy dif\u00edcil de desencadenar en la que una llamada do_mq_timedreceive puede regresar y dejar que do_mq_timedsend dependa de una direcci\u00f3n no v\u00e1lida, lo que provoca el siguiente bloqueo: RIP: 0010:wake_q_add_safe+0x13/0x60 Seguimiento de llamadas: __x64_sys_mq_timedsend+0x2a9/0x490 do_syscall_64+0x80 /0x680 Entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f5928e40343 La ejecuci\u00f3n ocurre como: 1. do_mq_timedreceive llama a wq_sleep con la direcci\u00f3n de `struct ext_wait_queue` en la pila de funciones (alias `ewq_addr` aqu\u00ed): contiene una `struct ext_wait_queue * v\u00e1lida ` siempre y cuando la pila no haya sido sobrescrita. 2. `ewq_addr` se agrega a info->e_wait_q[RECV].list en wq_add, y do_mq_timedsend lo recibe a trav\u00e9s de wq_get_first_waiter(info, RECV) para llamar a __pipelined_op. 3. El remitente llama a __pipelined_op::smp_store_release(&this->state, STATE_READY). Aqu\u00ed es donde comienza la ventana de ejecuci\u00f3n. (`esto` es `ewq_addr`.) 4. Si el receptor se activa ahora en do_mq_timedreceive::wq_sleep, ver\u00e1 `state == STATE_READY` y se interrumpir\u00e1. 5. do_mq_timedreceive regresa y ya no se garantiza que `ewq_addr` sea una `struct ext_wait_queue *` ya que estaba en la pila de do_mq_timedreceive. (Aunque es posible que la direcci\u00f3n no se sobrescriba hasta que otra funci\u00f3n la toque, lo que significa que puede persistir por un tiempo indefinido). 6. do_mq_timedsend::__pipelined_op() todav\u00eda cree que `ewq_addr` es una `struct ext_wait_queue *`, y lo usa para encontrar una task_struct para pasar a la llamada wake_q_add_safe. En el afortunado caso de que nada haya sobrescrito `ewq_addr` todav\u00eda, `ewq_addr->task` es la estructura de tarea correcta. En el desafortunado caso, __pipelined_op::wake_q_add_safe recibe una direcci\u00f3n falsa como la task_struct del receptor que causa el bloqueo. do_mq_timedsend::__pipelined_op() no debe eliminar la referencia a \"esto\" despu\u00e9s de configurar STATE_READY, ya que la contraparte del receptor ahora puede regresar. Cambie __pipelined_op para llamar a wake_q_add_safe en el task_struct del receptor devuelto por get_task_struct, en lugar de desreferenciar \"this\" que se encuentra en la pila del receptor. Como se\u00f1al\u00f3 Manfred, la ejecuci\u00f3n tambi\u00e9n existe potencialmente en ipc/msg.c::expunge_all e ipc/sem.c::wake_up_sem_queue_prepare. Arr\u00e9glelos de la misma manera."}], "id": "CVE-2021-47069", "lastModified": "2024-11-21T06:35:18.510", "metrics": {}, "published": "2024-03-01T22:15:46.857", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/4528c0c323085e645b8765913b4a7fd42cf49b65"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/807fa14536b26803b858da878b643be72952a097"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/a11ddb37bf367e6b5239b95ca759e5389bb46048"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://git.kernel.org/stable/c/4528c0c323085e645b8765913b4a7fd42cf49b65"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://git.kernel.org/stable/c/807fa14536b26803b858da878b643be72952a097"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://git.kernel.org/stable/c/a11ddb37bf367e6b5239b95ca759e5389bb46048"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Awaiting Analysis"}

{"affected_release": [{"advisory": "RHSA-2024:4352", "cpe": "cpe:/a:redhat:enterprise_linux:8::nfv", "package": "kernel-rt-0:4.18.0-553.8.1.rt7.349.el8_10", "product_name": "Red Hat Enterprise Linux 8", "release_date": "2024-07-08T00:00:00Z"}, {"advisory": "RHSA-2024:4211", "cpe": "cpe:/o:redhat:enterprise_linux:8", "package": "kernel-0:4.18.0-553.8.1.el8_10", "product_name": "Red Hat Enterprise Linux 8", "release_date": "2024-07-02T00:00:00Z"}, {"advisory": "RHSA-2024:5692", "cpe": "cpe:/o:redhat:rhel_aus:8.6", "package": "kernel-0:4.18.0-372.119.1.el8_6", "product_name": "Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support", "release_date": "2024-08-21T00:00:00Z"}, {"advisory": "RHSA-2024:5692", "cpe": "cpe:/o:redhat:rhel_tus:8.6", "package": "kernel-0:4.18.0-372.119.1.el8_6", "product_name": "Red Hat Enterprise Linux 8.6 Telecommunications Update Service", "release_date": "2024-08-21T00:00:00Z"}, {"advisory": "RHSA-2024:5692", "cpe": "cpe:/o:redhat:rhel_e4s:8.6", "package": "kernel-0:4.18.0-372.119.1.el8_6", "product_name": "Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions", "release_date": "2024-08-21T00:00:00Z"}, {"advisory": "RHSA-2024:6206", "cpe": "cpe:/o:redhat:rhel_eus:8.8", "package": "kernel-0:4.18.0-477.70.1.el8_8", "product_name": "Red Hat Enterprise Linux 8.8 Extended Update Support", "release_date": "2024-09-03T00:00:00Z"}], "bugzilla": {"description": "kernel: ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry", "id": "2267513", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2267513"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "verified"}, "cwe": "CWE-362", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry\ndo_mq_timedreceive calls wq_sleep with a stack local address. The\nsender (do_mq_timedsend) uses this address to later call pipelined_send.\nThis leads to a very hard to trigger race where a do_mq_timedreceive\ncall might return and leave do_mq_timedsend to rely on an invalid\naddress, causing the following crash:\nRIP: 0010:wake_q_add_safe+0x13/0x60\nCall Trace:\n__x64_sys_mq_timedsend+0x2a9/0x490\ndo_syscall_64+0x80/0x680\nentry_SYSCALL_64_after_hwframe+0x44/0xa9\nRIP: 0033:0x7f5928e40343\nThe race occurs as:\n1. do_mq_timedreceive calls wq_sleep with the address of `struct\next_wait_queue` on function stack (aliased as `ewq_addr` here) - it\nholds a valid `struct ext_wait_queue *` as long as the stack has not\nbeen overwritten.\n2. `ewq_addr` gets added to info->e_wait_q[RECV].list in wq_add, and\ndo_mq_timedsend receives it via wq_get_first_waiter(info, RECV) to call\n__pipelined_op.\n3. Sender calls __pipelined_op::smp_store_release(&this->state,\nSTATE_READY). Here is where the race window begins. (`this` is\n`ewq_addr`.)\n4. If the receiver wakes up now in do_mq_timedreceive::wq_sleep, it\nwill see `state == STATE_READY` and break.\n5. do_mq_timedreceive returns, and `ewq_addr` is no longer guaranteed\nto be a `struct ext_wait_queue *` since it was on do_mq_timedreceive's\nstack. (Although the address may not get overwritten until another\nfunction happens to touch it, which means it can persist around for an\nindefinite time.)\n6. do_mq_timedsend::__pipelined_op() still believes `ewq_addr` is a\n`struct ext_wait_queue *`, and uses it to find a task_struct to pass to\nthe wake_q_add_safe call. In the lucky case where nothing has\noverwritten `ewq_addr` yet, `ewq_addr->task` is the right task_struct.\nIn the unlucky case, __pipelined_op::wake_q_add_safe gets handed a\nbogus address as the receiver's task_struct causing the crash.\ndo_mq_timedsend::__pipelined_op() should not dereference `this` after\nsetting STATE_READY, as the receiver counterpart is now free to return.\nChange __pipelined_op to call wake_q_add_safe on the receiver's\ntask_struct returned by get_task_struct, instead of dereferencing `this`\nwhich sits on the receiver's stack.\nAs Manfred pointed out, the race potentially also exists in\nipc/msg.c::expunge_all and ipc/sem.c::wake_up_sem_queue_prepare. Fix\nthose in the same way.", "A flaw was found in the Linux kernel\u2019s IPC system. This flaw allows an attacker to use a specially crafted program to cause a rare race condition, leading to a denial of service."], "mitigation": {"lang": "en:us", "value": "Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible."}, "name": "CVE-2021-47069", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2024-03-01T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47069\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47069\nhttps://lore.kernel.org/linux-cve-announce/2024030141-CVE-2021-47069-5797@gregkh/T/#u"], "statement": "Red Hat Enterprise Linux 9 is not affected by this vulnerability.", "threat_severity": "Moderate"}