CVE-2025-21727: padata: fix UAF in padata_reorder
First published: Thu Feb 27 2025(Updated: )
In the Linux kernel, the following vulnerability has been resolved: padata: fix UAF in padata_reorder A bug was found when run ltp test: BUG: KASAN: slab-use-after-free in padata_find_next+0x29/0x1a0 Read of size 4 at addr ffff88bbfe003524 by task kworker/u113:2/3039206 CPU: 0 PID: 3039206 Comm: kworker/u113:2 Kdump: loaded Not tainted 6.6.0+ Workqueue: pdecrypt_parallel padata_parallel_worker Call Trace: <TASK> dump_stack_lvl+0x32/0x50 print_address_description.constprop.0+0x6b/0x3d0 print_report+0xdd/0x2c0 kasan_report+0xa5/0xd0 padata_find_next+0x29/0x1a0 padata_reorder+0x131/0x220 padata_parallel_worker+0x3d/0xc0 process_one_work+0x2ec/0x5a0 If 'mdelay(10)' is added before calling 'padata_find_next' in the 'padata_reorder' function, this issue could be reproduced easily with ltp test (pcrypt_aead01). This can be explained as bellow: pcrypt_aead_encrypt ... padata_do_parallel refcount_inc(&pd->refcnt); // add refcnt ... padata_do_serial padata_reorder // pd while (1) { padata_find_next(pd, true); // using pd queue_work_on ... padata_serial_worker crypto_del_alg padata_put_pd_cnt // sub refcnt padata_free_shell padata_put_pd(ps->pd); // pd is freed // loop again, but pd is freed // call padata_find_next, UAF } In the padata_reorder function, when it loops in 'while', if the alg is deleted, the refcnt may be decreased to 0 before entering 'padata_find_next', which leads to UAF. As mentioned in [1], do_serial is supposed to be called with BHs disabled and always happen under RCU protection, to address this issue, add synchronize_rcu() in 'padata_free_shell' wait for all _do_serial calls to finish. [1] https://lore.kernel.org/all/20221028160401.cccypv4euxikusiq@parnassus.localdomain/ [2] https://lore.kernel.org/linux-kernel/jfjz5d7zwbytztackem7ibzalm5lnxldi2eofeiczqmqs2m7o6@fq426cwnjtkm/
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | >6.6.0 | |
| Linux Kernel | >=5.4<5.10.235 | |
| Linux Kernel | >=5.11<5.15.179 | |
| Linux Kernel | >=5.16<6.1.129 | |
| Linux Kernel | >=6.2<6.6.76 | |
| Linux Kernel | >=6.7<6.12.13 | |
| Linux Kernel | >=6.13<6.13.2 |
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Reference Links
- https://git.kernel.org/stable/c/0ae2f332cfd2d74cf3ce344ec9938cf3e29c3ccd
- https://git.kernel.org/stable/c/573ac9c70bf7885dc85d82fa44550581bfc3b738
- https://git.kernel.org/stable/c/80231f069240d52e98b6a317456c67b2eafd0781
- https://git.kernel.org/stable/c/bbccae982e9fa1d7abcb23a5ec81cb0ec883f7de
- https://git.kernel.org/stable/c/e01780ea4661172734118d2a5f41bc9720765668
- https://git.kernel.org/stable/c/f78170bee51469734b1a306a74fc5f777bb22ba6
- https://git.kernel.org/stable/c/f3e0b9f790f8e8065d59e67b565a83154d9f3079
Frequently Asked Questions
What is the severity of CVE-2025-21727?
CVE-2025-21727 is classified as a high severity vulnerability due to the potential for use-after-free exploitation in the Linux kernel.
How do I fix CVE-2025-21727?
To fix CVE-2025-21727, update to the patched version of the Linux kernel, specifically version 6.6.0 or later.
What type of vulnerability is CVE-2025-21727?
CVE-2025-21727 is a use-after-free vulnerability identified in the padata component of the Linux kernel.
What are the symptoms of exploitation of CVE-2025-21727?
Exploitation of CVE-2025-21727 may result in unexpected system behavior or crashes, particularly under specific workloads.
Which software versions are affected by CVE-2025-21727?
CVE-2025-21727 affects the Linux kernel versions prior to 6.6.0.
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