From: Chen Ridong <chenridong@huawei.com> mainline inclusion from mainline-v6.14-rc1 commit e01780ea4661172734118d2a5f41bc9720765668 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBPBHS CVE: CVE-2025-21727 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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.locald... [2] https://lore.kernel.org/linux-kernel/jfjz5d7zwbytztackem7ibzalm5lnxldi2eofei... Fixes: b128a3040935 ("padata: allocate workqueue internally") Signed-off-by: Chen Ridong <chenridong@huawei.com> Signed-off-by: Qu Zicheng <quzicheng@huawei.com> Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- kernel/padata.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/padata.c b/kernel/padata.c index 9bf77b58ee08..6567ec3a6658 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -1118,6 +1118,12 @@ void padata_free_shell(struct padata_shell *ps) if (!ps) return; + /* + * Wait for all _do_serial calls to finish to avoid touching + * freed pd's and ps's. + */ + synchronize_rcu(); + mutex_lock(&ps->pinst->lock); list_del(&ps->list); pd = rcu_dereference_protected(ps->pd, 1); -- 2.34.1