ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry

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Summary

CVECVE-2021-47069
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-03-01 22:15:46 UTC
Updated2026-08-04 10:16:44 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 7 HIGH from [email protected]

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-672

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7HIGHCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected c5b2cbdbdac563f46ecd5e187253ab1abbd6fc04 4528c0c323085e645b8765913b4a7fd42cf49b65 git Not specified
CNA Linux Linux affected c5b2cbdbdac563f46ecd5e187253ab1abbd6fc04 807fa14536b26803b858da878b643be72952a097 git Not specified
CNA Linux Linux affected c5b2cbdbdac563f46ecd5e187253ab1abbd6fc04 a11ddb37bf367e6b5239b95ca759e5389bb46048 git Not specified
CNA Linux Linux affected 5.6 Not specified
CNA Linux Linux unaffected 5.6 semver Not specified
CNA Linux Linux unaffected 5.10.40 5.10.* semver Not specified
CNA Linux Linux unaffected 5.12.7 5.12.* semver Not specified
CNA Linux Linux unaffected 5.13 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a11ddb37bf367e6b5239b95ca759e5389bb46048 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
git.kernel.org/stable/c/807fa14536b26803b858da878b643be72952a097 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
git.kernel.org/stable/c/4528c0c323085e645b8765913b4a7fd42cf49b65 af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Legacy QID Mappings

  • 755966 SUSE Enterprise Linux Security Update for the linux kernel (SUSE-SU-2024:0857-1)
  • 756004 SUSE Enterprise Linux Security Update for the Linux Kernel (SUSE-SU-2024:0926-1)

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