bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel

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Summary

CVECVE-2024-26737
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-04-03 17:15:51 UTC
Updated2026-08-04 11:17:00 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel The following race is possible between bpf_timer_cancel_and_free and bpf_timer_cancel. It will lead a UAF on the timer->timer. bpf_timer_cancel(); spin_lock(); t = timer->time; spin_unlock(); bpf_timer_cancel_and_free(); spin_lock(); t = timer->timer; timer->timer = NULL; spin_unlock(); hrtimer_cancel(&t->timer); kfree(t); /* UAF on t */ hrtimer_cancel(&t->timer); In bpf_timer_cancel_and_free, this patch frees the timer->timer after a rcu grace period. This requires a rcu_head addition to the "struct bpf_hrtimer". Another kfree(t) happens in bpf_timer_init, this does not need a kfree_rcu because it is still under the spin_lock and timer->timer has not been visible by others yet. In bpf_timer_cancel, rcu_read_lock() is added because this helper can be used in a non rcu critical section context (e.g. from a sleepable bpf prog). Other timer->timer usages in helpers.c have been audited, bpf_timer_cancel() is the only place where timer->timer is used outside of the spin_lock. Another solution considered is to mark a t->flag in bpf_timer_cancel and clear it after hrtimer_cancel() is done. In bpf_timer_cancel_and_free, it busy waits for the flag to be cleared before kfree(t). This patch goes with a straight forward solution and frees timer->timer after a rcu grace period.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from ADP

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

Problem Types: CWE-416 | CWE-noinfo Not enough information

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 b00628b1c7d595ae5b544e059c27b1f5828314b4 5268bb02107b9eedfdcd51db75b407d10043368c git Not specified
CNA Linux Linux affected b00628b1c7d595ae5b544e059c27b1f5828314b4 addf5e297e6cbf5341f9c07720693ca9ba0057b5 git Not specified
CNA Linux Linux affected b00628b1c7d595ae5b544e059c27b1f5828314b4 8327ed12e8ebc5436bfaa1786c49988894f9c8a6 git Not specified
CNA Linux Linux affected b00628b1c7d595ae5b544e059c27b1f5828314b4 7d80a9e745fa5b47da3bca001f186c02485c7c33 git Not specified
CNA Linux Linux affected b00628b1c7d595ae5b544e059c27b1f5828314b4 0281b919e175bb9c3128bd3872ac2903e9436e3f git Not specified
CNA Linux Linux affected 5.15 Not specified
CNA Linux Linux unaffected 5.15 semver Not specified
CNA Linux Linux unaffected 5.15.150 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.80 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.19 6.6.* semver Not specified
CNA Linux Linux unaffected 6.7.7 6.7.* semver Not specified
CNA Linux Linux unaffected 6.8 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel - kernel/git/stable/linux.git - Linux kernel stable tree af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel - kernel/git/stable/linux.git - Linux kernel stable tree af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel - kernel/git/stable/linux.git - Linux kernel stable tree af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel - kernel/git/stable/linux.git - Linux kernel stable tree af854a3a-2127-422b-91ae-364da2661108 git.kernel.org Patch
bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel - kernel/git/stable/linux.git - Linux kernel stable tree 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

  • 6000567 Debian Security Update for linux (DSA 5658-1)

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