CVE-2021-47069 (GCVE-0-2021-47069)
Vulnerability from cvelistv5
Published
2024-03-01 21:15
Modified
2025-05-04 07:03
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry do_mq_timedreceive calls wq_sleep with a stack local address. The sender (do_mq_timedsend) uses this address to later call pipelined_send. This leads to a very hard to trigger race where a do_mq_timedreceive call might return and leave do_mq_timedsend to rely on an invalid address, causing the following crash: RIP: 0010:wake_q_add_safe+0x13/0x60 Call Trace: __x64_sys_mq_timedsend+0x2a9/0x490 do_syscall_64+0x80/0x680 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f5928e40343 The race occurs as: 1. do_mq_timedreceive calls wq_sleep with the address of `struct ext_wait_queue` on function stack (aliased as `ewq_addr` here) - it holds a valid `struct ext_wait_queue *` as long as the stack has not been overwritten. 2. `ewq_addr` gets added to info->e_wait_q[RECV].list in wq_add, and do_mq_timedsend receives it via wq_get_first_waiter(info, RECV) to call __pipelined_op. 3. Sender calls __pipelined_op::smp_store_release(&this->state, STATE_READY). Here is where the race window begins. (`this` is `ewq_addr`.) 4. If the receiver wakes up now in do_mq_timedreceive::wq_sleep, it will see `state == STATE_READY` and break. 5. do_mq_timedreceive returns, and `ewq_addr` is no longer guaranteed to be a `struct ext_wait_queue *` since it was on do_mq_timedreceive's stack. (Although the address may not get overwritten until another function happens to touch it, which means it can persist around for an indefinite time.) 6. do_mq_timedsend::__pipelined_op() still believes `ewq_addr` is a `struct ext_wait_queue *`, and uses it to find a task_struct to pass to the wake_q_add_safe call. In the lucky case where nothing has overwritten `ewq_addr` yet, `ewq_addr->task` is the right task_struct. In the unlucky case, __pipelined_op::wake_q_add_safe gets handed a bogus address as the receiver's task_struct causing the crash. do_mq_timedsend::__pipelined_op() should not dereference `this` after setting STATE_READY, as the receiver counterpart is now free to return. Change __pipelined_op to call wake_q_add_safe on the receiver's task_struct returned by get_task_struct, instead of dereferencing `this` which sits on the receiver's stack. As Manfred pointed out, the race potentially also exists in ipc/msg.c::expunge_all and ipc/sem.c::wake_up_sem_queue_prepare. Fix those in the same way.
References
Impacted products
Vendor Product Version
Linux Linux Version: c5b2cbdbdac563f46ecd5e187253ab1abbd6fc04
Version: c5b2cbdbdac563f46ecd5e187253ab1abbd6fc04
Version: c5b2cbdbdac563f46ecd5e187253ab1abbd6fc04
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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-\u003ee_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(\u0026this-\u003estate,\\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\u0027s\\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-\u003etask` 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\u0027s 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\u0027s\\ntask_struct returned by get_task_struct, instead of dereferencing `this`\\nwhich sits on the receiver\u0027s 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-\u0026gt;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(\u0026amp;this-\u0026gt;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-\u0026gt;task` es la estructura de tarea correcta. 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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-\u003ee_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(\u0026this-\u003estate,\\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\u0027s\\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-\u003etask` 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\u0027s 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\u0027s\\ntask_struct returned by get_task_struct, instead of dereferencing `this`\\nwhich sits on the receiver\u0027s 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.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.40\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.12.7\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.13\", \"versionStartIncluding\": \"5.6\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2025-05-04T07:03:33.104Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47069\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2025-05-04T07:03:33.104Z\", \"dateReserved\": \"2024-02-29T22:33:44.296Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-03-01T21:15:08.598Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}


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