{"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":"2025-05-04T07:03:33.104Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2025-05-04T07:03:33.104Z"},"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":"c5b2cbdbdac563f46ecd5e187253ab1abbd6fc04","lessThan":"4528c0c323085e645b8765913b4a7fd42cf49b65","status":"affected","versionType":"git"},{"version":"c5b2cbdbdac563f46ecd5e187253ab1abbd6fc04","lessThan":"807fa14536b26803b858da878b643be72952a097","status":"affected","versionType":"git"},{"version":"c5b2cbdbdac563f46ecd5e187253ab1abbd6fc04","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"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"5.10.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"5.12.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"5.13"}]}]}],"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-1.2.0"}},"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"]}]}]}}