Updated: 2025-02-04 15:45:17.545814
Description:
In the Linux kernel, the following vulnerability has been resolved: padata: Fix refcnt handling in padata_free_shell() In a high-load arm64 environment, the pcrypt_aead01 test in LTP can lead to system UAF (Use-After-Free) issues. Due to the lengthy analysis of the pcrypt_aead01 function call, I'll describe the problem scenario using a simplified model: Suppose there's a user of padata named `user_function` that adheres to the padata requirement of calling `padata_free_shell` after `serial()` has been invoked, as demonstrated in the following code: ```c struct request { struct padata_priv padata; struct completion *done; }; void parallel(struct padata_priv *padata) { do_something(); } void serial(struct padata_priv *padata) { struct request *request = container_of(padata, struct request, padata); complete(request->done); } void user_function() { DECLARE_COMPLETION(done) padata->parallel = parallel; padata->serial = serial; padata_do_parallel(); wait_for_completion(&done); padata_free_shell(); } ``` In the corresponding padata.c file, there's the following code: ```c static void padata_serial_worker(struct work_struct *serial_work) { ... cnt = 0; while (!list_empty(&local_list)) { ... padata->serial(padata); cnt++; } local_bh_enable(); if (refcount_sub_and_test(cnt, &pd->refcnt)) padata_free_pd(pd); } ``` Because of the high system load and the accumulation of unexecuted softirq at this moment, `local_bh_enable()` in padata takes longer to execute than usual. Subsequently, when accessing `pd->refcnt`, `pd` has already been released by `padata_free_shell()`, resulting in a UAF issue with `pd->refcnt`. The fix is straightforward: add `refcount_dec_and_test` before calling `padata_free_pd` in `padata_free_shell`.
Links | NIST | CIRCL | RHEL | Ubuntu |
Severity | Score | |
---|---|---|
CVSS Version 2.x | 0 | |
CVSS Version 3.x | HIGH | 7.8 |
OS name | Project name | Version | Score | Severity | Status | Errata | Last updated | Statement |
---|---|---|---|---|---|---|---|---|
AlmaLinux 9.2 ESU | kernel | 5.14.0 | 7.8 | HIGH | Needs Triage | 2025-02-04 11:16:31 | ||
AlmaLinux 9.2 FIPS | kernel | 5.14.0 | 7.8 | HIGH | Needs Triage | 2025-02-04 11:16:30 | ||
Ubuntu 16.04 ELS | linux-hwe | 4.15.0 | 7.8 | HIGH | In Progress | 2025-02-07 06:34:15 | ||
Ubuntu 18.04 ELS | linux | 4.15.0 | 7.8 | HIGH | In Progress | 2025-02-07 22:53:38 |