{"api_version":"1","generated_at":"2026-07-23T17:11:08+00:00","cve":"CVE-2025-21727","urls":{"html":"https://cve.report/CVE-2025-21727","api":"https://cve.report/api/cve/CVE-2025-21727.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2025-21727","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2025-21727"},"summary":{"title":"padata: fix UAF in padata_reorder","description":"In the Linux kernel, the following vulnerability has been resolved:\n\npadata: fix UAF in padata_reorder\n\nA bug was found when run ltp test:\n\nBUG: KASAN: slab-use-after-free in padata_find_next+0x29/0x1a0\nRead of size 4 at addr ffff88bbfe003524 by task kworker/u113:2/3039206\n\nCPU: 0 PID: 3039206 Comm: kworker/u113:2 Kdump: loaded Not tainted 6.6.0+\nWorkqueue: pdecrypt_parallel padata_parallel_worker\nCall Trace:\n<TASK>\ndump_stack_lvl+0x32/0x50\nprint_address_description.constprop.0+0x6b/0x3d0\nprint_report+0xdd/0x2c0\nkasan_report+0xa5/0xd0\npadata_find_next+0x29/0x1a0\npadata_reorder+0x131/0x220\npadata_parallel_worker+0x3d/0xc0\nprocess_one_work+0x2ec/0x5a0\n\nIf 'mdelay(10)' is added before calling 'padata_find_next' in the\n'padata_reorder' function, this issue could be reproduced easily with\nltp test (pcrypt_aead01).\n\nThis can be explained as bellow:\n\npcrypt_aead_encrypt\n...\npadata_do_parallel\nrefcount_inc(&pd->refcnt); // add refcnt\n...\npadata_do_serial\npadata_reorder // pd\nwhile (1) {\npadata_find_next(pd, true); // using pd\nqueue_work_on\n...\npadata_serial_worker\t\t\t\tcrypto_del_alg\npadata_put_pd_cnt // sub refcnt\n\t\t\t\t\t\tpadata_free_shell\n\t\t\t\t\t\tpadata_put_pd(ps->pd);\n\t\t\t\t\t\t// pd is freed\n// loop again, but pd is freed\n// call padata_find_next, UAF\n}\n\nIn the padata_reorder function, when it loops in 'while', if the alg is\ndeleted, the 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the Linux kernel, the following vulnerability has been resolved:\n\npadata: fix UAF in padata_reorder\n\nA bug was found when run ltp test:\n\nBUG: KASAN: slab-use-after-free in padata_find_next+0x29/0x1a0\nRead of size 4 at addr ffff88bbfe003524 by task kworker/u113:2/3039206\n\nCPU: 0 PID: 3039206 Comm: kworker/u113:2 Kdump: loaded Not tainted 6.6.0+\nWorkqueue: pdecrypt_parallel padata_parallel_worker\nCall Trace:\n<TASK>\ndump_stack_lvl+0x32/0x50\nprint_address_description.constprop.0+0x6b/0x3d0\nprint_report+0xdd/0x2c0\nkasan_report+0xa5/0xd0\npadata_find_next+0x29/0x1a0\npadata_reorder+0x131/0x220\npadata_parallel_worker+0x3d/0xc0\nprocess_one_work+0x2ec/0x5a0\n\nIf 'mdelay(10)' is added before calling 'padata_find_next' in the\n'padata_reorder' function, this issue could be reproduced easily with\nltp test (pcrypt_aead01).\n\nThis can be explained as bellow:\n\npcrypt_aead_encrypt\n...\npadata_do_parallel\nrefcount_inc(&pd->refcnt); // add refcnt\n...\npadata_do_serial\npadata_reorder // pd\nwhile (1) {\npadata_find_next(pd, true); // using pd\nqueue_work_on\n...\npadata_serial_worker\t\t\t\tcrypto_del_alg\npadata_put_pd_cnt // sub refcnt\n\t\t\t\t\t\tpadata_free_shell\n\t\t\t\t\t\tpadata_put_pd(ps->pd);\n\t\t\t\t\t\t// pd is freed\n// loop again, but pd is freed\n// call padata_find_next, UAF\n}\n\nIn the padata_reorder function, when it loops in 'while', if the alg is\ndeleted, the refcnt may be decreased to 0 before entering\n'padata_find_next', which leads to UAF.\n\nAs mentioned in [1], do_serial is supposed to be called with BHs disabled\nand always happen under RCU protection, to address this issue, add\nsynchronize_rcu() in 'padata_free_shell' wait for all _do_serial calls\nto finish.\n\n[1] https://lore.kernel.org/all/20221028160401.cccypv4euxikusiq@parnassus.localdomain/\n[2] 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fix UAF in padata_reorder","CVE":"CVE-2025-21727","Year":"2025"},"notes":[{"CveYear":"2025","CveId":"21727","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\npadata: fix UAF in padata_reorder\n\nA bug was found when run ltp test:\n\nBUG: KASAN: slab-use-after-free in padata_find_next+0x29/0x1a0\nRead of size 4 at addr ffff88bbfe003524 by task kworker/u113:2/3039206\n\nCPU: 0 PID: 3039206 Comm: kworker/u113:2 Kdump: loaded Not tainted 6.6.0+\nWorkqueue: pdecrypt_parallel padata_parallel_worker\nCall Trace:\n<TASK>\ndump_stack_lvl+0x32/0x50\nprint_address_description.constprop.0+0x6b/0x3d0\nprint_report+0xdd/0x2c0\nkasan_report+0xa5/0xd0\npadata_find_next+0x29/0x1a0\npadata_reorder+0x131/0x220\npadata_parallel_worker+0x3d/0xc0\nprocess_one_work+0x2ec/0x5a0\n\nIf 'mdelay(10)' is added before calling 'padata_find_next' in the\n'padata_reorder' function, this issue could be reproduced easily with\nltp test (pcrypt_aead01).\n\nThis can be explained as bellow:\n\npcrypt_aead_encrypt\n...\npadata_do_parallel\nrefcount_inc(&pd->refcnt); // add refcnt\n...\npadata_do_serial\npadata_reorder // pd\nwhile (1) {\npadata_find_next(pd, true); // using pd\nqueue_work_on\n...\npadata_serial_worker\t\t\t\tcrypto_del_alg\npadata_put_pd_cnt // sub refcnt\n\t\t\t\t\t\tpadata_free_shell\n\t\t\t\t\t\tpadata_put_pd(ps->pd);\n\t\t\t\t\t\t// pd is freed\n// loop again, but pd is freed\n// call padata_find_next, UAF\n}\n\nIn the padata_reorder function, when it loops in 'while', if the alg is\ndeleted, the refcnt may be decreased to 0 before entering\n'padata_find_next', which leads to UAF.\n\nAs mentioned in [1], do_serial is supposed to be called with BHs disabled\nand always happen under RCU protection, to address this issue, add\nsynchronize_rcu() in 'padata_free_shell' wait for all _do_serial calls\nto finish.\n\n[1] https://lore.kernel.org/all/20221028160401.cccypv4euxikusiq@parnassus.localdomain/\n[2] https://lore.kernel.org/linux-kernel/jfjz5d7zwbytztackem7ibzalm5lnxldi2eofeiczqmqs2m7o6@fq426cwnjtkm/","Type":"Description","Title":"padata: fix UAF in padata_reorder"}]}}}