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CVE-2025-21631 (GCVE-0-2025-21631)

Vulnerability from cvelistv5 – Published: 2025-01-19 10:17 – Updated: 2026-08-05 11:53
VLAI
Title
block, bfq: fix waker_bfqq UAF after bfq_split_bfqq()
Summary
In the Linux kernel, the following vulnerability has been resolved: block, bfq: fix waker_bfqq UAF after bfq_split_bfqq() Our syzkaller report a following UAF for v6.6: BUG: KASAN: slab-use-after-free in bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958 Read of size 8 at addr ffff8881b57147d8 by task fsstress/232726 CPU: 2 PID: 232726 Comm: fsstress Not tainted 6.6.0-g3629d1885222 #39 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x91/0xf0 lib/dump_stack.c:106 print_address_description.constprop.0+0x66/0x300 mm/kasan/report.c:364 print_report+0x3e/0x70 mm/kasan/report.c:475 kasan_report+0xb8/0xf0 mm/kasan/report.c:588 hlist_add_head include/linux/list.h:1023 [inline] bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958 bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271 bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323 blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660 blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143 __submit_bio+0xa0/0x6b0 block/blk-core.c:639 __submit_bio_noacct_mq block/blk-core.c:718 [inline] submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747 submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847 __ext4_read_bh fs/ext4/super.c:205 [inline] ext4_read_bh+0x15e/0x2e0 fs/ext4/super.c:230 __read_extent_tree_block+0x304/0x6f0 fs/ext4/extents.c:567 ext4_find_extent+0x479/0xd20 fs/ext4/extents.c:947 ext4_ext_map_blocks+0x1a3/0x2680 fs/ext4/extents.c:4182 ext4_map_blocks+0x929/0x15a0 fs/ext4/inode.c:660 ext4_iomap_begin_report+0x298/0x480 fs/ext4/inode.c:3569 iomap_iter+0x3dd/0x1010 fs/iomap/iter.c:91 iomap_fiemap+0x1f4/0x360 fs/iomap/fiemap.c:80 ext4_fiemap+0x181/0x210 fs/ext4/extents.c:5051 ioctl_fiemap.isra.0+0x1b4/0x290 fs/ioctl.c:220 do_vfs_ioctl+0x31c/0x11a0 fs/ioctl.c:811 __do_sys_ioctl fs/ioctl.c:869 [inline] __se_sys_ioctl+0xae/0x190 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x70/0x120 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x78/0xe2 Allocated by task 232719: kasan_save_stack+0x22/0x50 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 __kasan_slab_alloc+0x87/0x90 mm/kasan/common.c:328 kasan_slab_alloc include/linux/kasan.h:188 [inline] slab_post_alloc_hook mm/slab.h:768 [inline] slab_alloc_node mm/slub.c:3492 [inline] kmem_cache_alloc_node+0x1b8/0x6f0 mm/slub.c:3537 bfq_get_queue+0x215/0x1f00 block/bfq-iosched.c:5869 bfq_get_bfqq_handle_split+0x167/0x5f0 block/bfq-iosched.c:6776 bfq_init_rq+0x13a4/0x17a0 block/bfq-iosched.c:6938 bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271 bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323 blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660 blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143 __submit_bio+0xa0/0x6b0 block/blk-core.c:639 __submit_bio_noacct_mq block/blk-core.c:718 [inline] submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747 submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847 __ext4_read_bh fs/ext4/super.c:205 [inline] ext4_read_bh_nowait+0x15a/0x240 fs/ext4/super.c:217 ext4_read_bh_lock+0xac/0xd0 fs/ext4/super.c:242 ext4_bread_batch+0x268/0x500 fs/ext4/inode.c:958 __ext4_find_entry+0x448/0x10f0 fs/ext4/namei.c:1671 ext4_lookup_entry fs/ext4/namei.c:1774 [inline] ext4_lookup.part.0+0x359/0x6f0 fs/ext4/namei.c:1842 ext4_lookup+0x72/0x90 fs/ext4/namei.c:1839 __lookup_slow+0x257/0x480 fs/namei.c:1696 lookup_slow fs/namei.c:1713 [inline] walk_component+0x454/0x5c0 fs/namei.c:2004 link_path_walk.part.0+0x773/0xda0 fs/namei.c:2331 link_path_walk fs/namei.c:3826 [inline] path_openat+0x1b9/0x520 fs/namei.c:3826 do_filp_open+0x1b7/0x400 fs/namei.c:3857 do_sys_openat2+0x5dc/0x6e0 fs/open.c:1428 do_sys_open fs/open.c:1443 [inline] __do_sys_openat fs/open.c:1459 [inline] __se_sys_openat fs/open.c:1454 [inline] __x64_sys_openat+0x148/0x200 fs/open.c:1454 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_6 ---truncated---
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-02-10 17:11 UTC
CWE
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 63a07379fdb6c72450cb05294461c6016b8b7726 , < f587c1ac68956c4703857d650d9b1cd7bb2ac4d7 (git)
Affected: de0456460f2abf921e356ed2bd8da87a376680bd , < 2550149fcdf2934155ff625d76ad4e3d4b25bbc6 (git)
Affected: 0780451f03bf518bc032a7c584de8f92e2d39d7f , < be3eed59ac01f429ac10aaa46e26f653bcf581ab (git)
Affected: 1ba0403ac6447f2d63914fb760c44a3b19c44eaf , < bc2aeb35ff167e0c6b0cedf0c96a5c41e6cba1ed (git)
Affected: 1ba0403ac6447f2d63914fb760c44a3b19c44eaf , < fcede1f0a043ccefe9bc6ad57f12718e42f63f1d (git)
Affected: 0b8bda0ff17156cd3f60944527c9d8c9f99f1583 (git)
Affected: cae58d19121a70329cf971359e2518c93fec04fe (git)
Affected: 5.15.168 , < 5.15.177 (semver)
Affected: 6.1.113 , < 6.1.125 (semver)
Affected: 6.6.54 , < 6.6.72 (semver)
Affected: 6.10.13 , < 6.11 (semver)
Affected: 6.11.2 , < 6.12 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (semver)
Unaffected: 5.15.177 , ≤ 5.15.* (semver)
Unaffected: 6.1.125 , ≤ 6.1.* (semver)
Unaffected: 6.6.72 , ≤ 6.6.* (semver)
Unaffected: 6.12.10 , ≤ 6.12.* (semver)
Unaffected: 6.13 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblock, bfq: fix waker_bfqq UAF after bfq_split_bfqq()\n\nOur syzkaller report a following UAF for v6.6:\n\nBUG: KASAN: slab-use-after-free in bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958\nRead of size 8 at addr ffff8881b57147d8 by task fsstress/232726\n\nCPU: 2 PID: 232726 Comm: fsstress Not tainted 6.6.0-g3629d1885222 #39\nCall Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:88 [inline]\n dump_stack_lvl+0x91/0xf0 lib/dump_stack.c:106\n print_address_description.constprop.0+0x66/0x300 mm/kasan/report.c:364\n print_report+0x3e/0x70 mm/kasan/report.c:475\n kasan_report+0xb8/0xf0 mm/kasan/report.c:588\n hlist_add_head include/linux/list.h:1023 [inline]\n bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958\n bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271\n bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323\n blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660\n blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143\n __submit_bio+0xa0/0x6b0 block/blk-core.c:639\n __submit_bio_noacct_mq block/blk-core.c:718 [inline]\n submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747\n submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847\n __ext4_read_bh fs/ext4/super.c:205 [inline]\n ext4_read_bh+0x15e/0x2e0 fs/ext4/super.c:230\n __read_extent_tree_block+0x304/0x6f0 fs/ext4/extents.c:567\n ext4_find_extent+0x479/0xd20 fs/ext4/extents.c:947\n ext4_ext_map_blocks+0x1a3/0x2680 fs/ext4/extents.c:4182\n ext4_map_blocks+0x929/0x15a0 fs/ext4/inode.c:660\n ext4_iomap_begin_report+0x298/0x480 fs/ext4/inode.c:3569\n iomap_iter+0x3dd/0x1010 fs/iomap/iter.c:91\n iomap_fiemap+0x1f4/0x360 fs/iomap/fiemap.c:80\n ext4_fiemap+0x181/0x210 fs/ext4/extents.c:5051\n ioctl_fiemap.isra.0+0x1b4/0x290 fs/ioctl.c:220\n do_vfs_ioctl+0x31c/0x11a0 fs/ioctl.c:811\n __do_sys_ioctl fs/ioctl.c:869 [inline]\n __se_sys_ioctl+0xae/0x190 fs/ioctl.c:857\n do_syscall_x64 arch/x86/entry/common.c:51 [inline]\n do_syscall_64+0x70/0x120 arch/x86/entry/common.c:81\n entry_SYSCALL_64_after_hwframe+0x78/0xe2\n\nAllocated by task 232719:\n kasan_save_stack+0x22/0x50 mm/kasan/common.c:45\n kasan_set_track+0x25/0x30 mm/kasan/common.c:52\n __kasan_slab_alloc+0x87/0x90 mm/kasan/common.c:328\n kasan_slab_alloc include/linux/kasan.h:188 [inline]\n slab_post_alloc_hook mm/slab.h:768 [inline]\n slab_alloc_node mm/slub.c:3492 [inline]\n kmem_cache_alloc_node+0x1b8/0x6f0 mm/slub.c:3537\n bfq_get_queue+0x215/0x1f00 block/bfq-iosched.c:5869\n bfq_get_bfqq_handle_split+0x167/0x5f0 block/bfq-iosched.c:6776\n bfq_init_rq+0x13a4/0x17a0 block/bfq-iosched.c:6938\n bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271\n bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323\n blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660\n blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143\n __submit_bio+0xa0/0x6b0 block/blk-core.c:639\n __submit_bio_noacct_mq block/blk-core.c:718 [inline]\n submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747\n submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847\n __ext4_read_bh fs/ext4/super.c:205 [inline]\n ext4_read_bh_nowait+0x15a/0x240 fs/ext4/super.c:217\n ext4_read_bh_lock+0xac/0xd0 fs/ext4/super.c:242\n ext4_bread_batch+0x268/0x500 fs/ext4/inode.c:958\n __ext4_find_entry+0x448/0x10f0 fs/ext4/namei.c:1671\n ext4_lookup_entry fs/ext4/namei.c:1774 [inline]\n ext4_lookup.part.0+0x359/0x6f0 fs/ext4/namei.c:1842\n ext4_lookup+0x72/0x90 fs/ext4/namei.c:1839\n __lookup_slow+0x257/0x480 fs/namei.c:1696\n lookup_slow fs/namei.c:1713 [inline]\n walk_component+0x454/0x5c0 fs/namei.c:2004\n link_path_walk.part.0+0x773/0xda0 fs/namei.c:2331\n link_path_walk fs/namei.c:3826 [inline]\n path_openat+0x1b9/0x520 fs/namei.c:3826\n do_filp_open+0x1b7/0x400 fs/namei.c:3857\n do_sys_openat2+0x5dc/0x6e0 fs/open.c:1428\n do_sys_open fs/open.c:1443 [inline]\n __do_sys_openat fs/open.c:1459 [inline]\n __se_sys_openat fs/open.c:1454 [inline]\n __x64_sys_openat+0x148/0x200 fs/open.c:1454\n do_syscall_x64 arch/x86/entry/common.c:51 [inline]\n do_syscall_6\n---truncated---"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
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              "value": "AV:L - The vulnerable code is the BFQ I/O scheduler, reached through ordinary local syscalls (read/write/openat/ioctl) that submit block I/O via submit_bio() \u2192 blk_mq_submit_bio() \u2192 bfq_insert_requests() \u2192 bfq_init_rq(). No remote data is processed by this path.\nAC:L - The free (bfq_split_bfqq \u2192 bfq_release_process_ref \u2192 bfq_put_queue) and the use (hlist_add_head on the dangling waker_bfqq) occur in the same task within a single bfq_init_rq() call, so there is no race window to win; the attacker fully controls the preconditions (cooperating-queue merge, split_coop, and waker detection) by spawning their own processes with a chosen I/O pattern, and syzkaller hit it with plain fsstress.\nPR:L - Any unprivileged local user can trigger this with normal file I/O on a BFQ-scheduled device \u2014 there is no capability check anywhere along bfq_prepare_request/bfq_init_rq/bfq_get_bfqq_handle_split, and it is reachable from inside containers and restricted sandboxes.\nUI:N - The attacker\u0027s own I/O workload creates the queue-merge, split, and waker-detection state; no action by any other user or victim process is needed.\nS:U - The use-after-free corrupts kernel heap memory within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The freed bfq_queue is reallocated from the bfq_pool slab and its contents are read back (h-\u003efirst in hlist_add_head, and later bfqq-\u003ewaker_bfqq-\u003enext_rq / budget reads in bfq_select_queue), giving a controllable kernel-memory disclosure primitive that can leak heap pointers and defeat KASLR.\nI:H - hlist_add_head() on the freed object performs WRITE_ONCE(first-\u003epprev, \u0026n-\u003enext), writing a live kernel heap pointer to an address taken from attacker-reclaimed memory \u2014 an arbitrary-write primitive \u2014 plus writes into the freed object itself, which is exploitable for privilege escalation.\nA:H - The use-after-free reliably corrupts the bfq_pool slab and the scheduler\u0027s woken_list, producing KASAN splats, list corruption, and kernel panics in the block layer, halting the system."
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        {
          "url": "https://git.kernel.org/stable/c/fcede1f0a043ccefe9bc6ad57f12718e42f63f1d"
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblock, bfq: fix waker_bfqq UAF after bfq_split_bfqq()\n\nOur syzkaller report a following UAF for v6.6:\n\nBUG: KASAN: slab-use-after-free in bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958\nRead of size 8 at addr ffff8881b57147d8 by task fsstress/232726\n\nCPU: 2 PID: 232726 Comm: fsstress Not tainted 6.6.0-g3629d1885222 #39\nCall Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:88 [inline]\n dump_stack_lvl+0x91/0xf0 lib/dump_stack.c:106\n print_address_description.constprop.0+0x66/0x300 mm/kasan/report.c:364\n print_report+0x3e/0x70 mm/kasan/report.c:475\n kasan_report+0xb8/0xf0 mm/kasan/report.c:588\n hlist_add_head include/linux/list.h:1023 [inline]\n bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958\n bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271\n bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323\n blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660\n blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143\n __submit_bio+0xa0/0x6b0 block/blk-core.c:639\n __submit_bio_noacct_mq block/blk-core.c:718 [inline]\n submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747\n submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847\n __ext4_read_bh fs/ext4/super.c:205 [inline]\n ext4_read_bh+0x15e/0x2e0 fs/ext4/super.c:230\n __read_extent_tree_block+0x304/0x6f0 fs/ext4/extents.c:567\n ext4_find_extent+0x479/0xd20 fs/ext4/extents.c:947\n ext4_ext_map_blocks+0x1a3/0x2680 fs/ext4/extents.c:4182\n ext4_map_blocks+0x929/0x15a0 fs/ext4/inode.c:660\n ext4_iomap_begin_report+0x298/0x480 fs/ext4/inode.c:3569\n iomap_iter+0x3dd/0x1010 fs/iomap/iter.c:91\n iomap_fiemap+0x1f4/0x360 fs/iomap/fiemap.c:80\n ext4_fiemap+0x181/0x210 fs/ext4/extents.c:5051\n ioctl_fiemap.isra.0+0x1b4/0x290 fs/ioctl.c:220\n do_vfs_ioctl+0x31c/0x11a0 fs/ioctl.c:811\n __do_sys_ioctl fs/ioctl.c:869 [inline]\n __se_sys_ioctl+0xae/0x190 fs/ioctl.c:857\n do_syscall_x64 arch/x86/entry/common.c:51 [inline]\n do_syscall_64+0x70/0x120 arch/x86/entry/common.c:81\n entry_SYSCALL_64_after_hwframe+0x78/0xe2\n\nAllocated by task 232719:\n kasan_save_stack+0x22/0x50 mm/kasan/common.c:45\n kasan_set_track+0x25/0x30 mm/kasan/common.c:52\n __kasan_slab_alloc+0x87/0x90 mm/kasan/common.c:328\n kasan_slab_alloc include/linux/kasan.h:188 [inline]\n slab_post_alloc_hook mm/slab.h:768 [inline]\n slab_alloc_node mm/slub.c:3492 [inline]\n kmem_cache_alloc_node+0x1b8/0x6f0 mm/slub.c:3537\n bfq_get_queue+0x215/0x1f00 block/bfq-iosched.c:5869\n bfq_get_bfqq_handle_split+0x167/0x5f0 block/bfq-iosched.c:6776\n bfq_init_rq+0x13a4/0x17a0 block/bfq-iosched.c:6938\n bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271\n bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323\n blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660\n blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143\n __submit_bio+0xa0/0x6b0 block/blk-core.c:639\n __submit_bio_noacct_mq block/blk-core.c:718 [inline]\n submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747\n submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847\n __ext4_read_bh fs/ext4/super.c:205 [inline]\n ext4_read_bh_nowait+0x15a/0x240 fs/ext4/super.c:217\n ext4_read_bh_lock+0xac/0xd0 fs/ext4/super.c:242\n ext4_bread_batch+0x268/0x500 fs/ext4/inode.c:958\n __ext4_find_entry+0x448/0x10f0 fs/ext4/namei.c:1671\n ext4_lookup_entry fs/ext4/namei.c:1774 [inline]\n ext4_lookup.part.0+0x359/0x6f0 fs/ext4/namei.c:1842\n ext4_lookup+0x72/0x90 fs/ext4/namei.c:1839\n __lookup_slow+0x257/0x480 fs/namei.c:1696\n lookup_slow fs/namei.c:1713 [inline]\n walk_component+0x454/0x5c0 fs/namei.c:2004\n link_path_walk.part.0+0x773/0xda0 fs/namei.c:2331\n link_path_walk fs/namei.c:3826 [inline]\n path_openat+0x1b9/0x520 fs/namei.c:3826\n do_filp_open+0x1b7/0x400 fs/namei.c:3857\n do_sys_openat2+0x5dc/0x6e0 fs/open.c:1428\n do_sys_open fs/open.c:1443 [inline]\n __do_sys_openat fs/open.c:1459 [inline]\n __se_sys_openat fs/open.c:1454 [inline]\n __x64_sys_openat+0x148/0x200 fs/open.c:1454\n do_syscall_x64 arch/x86/entry/common.c:51 [inline]\n do_syscall_6\n---truncated---"
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: block, bfq: fix waker_bfqq UAF after bfq_split_bfqq() Our syzkaller report a following UAF for v6.6: BUG: KASAN: slab-use-after-free in bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958 Read of size 8 at addr ffff8881b57147d8 by task fsstress/232726 CPU: 2 PID: 232726 Comm: fsstress Not tainted 6.6.0-g3629d1885222 #39 Call Trace:  __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x91/0xf0 lib/dump_stack.c:106 print_address_description.constprop.0+0x66/0x300 mm/kasan/report.c:364 print_report+0x3e/0x70 mm/kasan/report.c:475 kasan_report+0xb8/0xf0 mm/kasan/report.c:588 hlist_add_head include/linux/list.h:1023 [inline] bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958 bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271 bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323 blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660 blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143 __submit_bio+0xa0/0x6b0 block/blk-core.c:639 __submit_bio_noacct_mq block/blk-core.c:718 [inline] submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747 submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847 __ext4_read_bh fs/ext4/super.c:205 [inline] ext4_read_bh+0x15e/0x2e0 fs/ext4/super.c:230 __read_extent_tree_block+0x304/0x6f0 fs/ext4/extents.c:567 ext4_find_extent+0x479/0xd20 fs/ext4/extents.c:947 ext4_ext_map_blocks+0x1a3/0x2680 fs/ext4/extents.c:4182 ext4_map_blocks+0x929/0x15a0 fs/ext4/inode.c:660 ext4_iomap_begin_report+0x298/0x480 fs/ext4/inode.c:3569 iomap_iter+0x3dd/0x1010 fs/iomap/iter.c:91 iomap_fiemap+0x1f4/0x360 fs/iomap/fiemap.c:80 ext4_fiemap+0x181/0x210 fs/ext4/extents.c:5051 ioctl_fiemap.isra.0+0x1b4/0x290 fs/ioctl.c:220 do_vfs_ioctl+0x31c/0x11a0 fs/ioctl.c:811 __do_sys_ioctl fs/ioctl.c:869 [inline] __se_sys_ioctl+0xae/0x190 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x70/0x120 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x78/0xe2 Allocated by task 232719: kasan_save_stack+0x22/0x50 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 __kasan_slab_alloc+0x87/0x90 mm/kasan/common.c:328 kasan_slab_alloc include/linux/kasan.h:188 [inline] slab_post_alloc_hook mm/slab.h:768 [inline] slab_alloc_node mm/slub.c:3492 [inline] kmem_cache_alloc_node+0x1b8/0x6f0 mm/slub.c:3537 bfq_get_queue+0x215/0x1f00 block/bfq-iosched.c:5869 bfq_get_bfqq_handle_split+0x167/0x5f0 block/bfq-iosched.c:6776 bfq_init_rq+0x13a4/0x17a0 block/bfq-iosched.c:6938 bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271 bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323 blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660 blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143 __submit_bio+0xa0/0x6b0 block/blk-core.c:639 __submit_bio_noacct_mq block/blk-core.c:718 [inline] submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747 submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847 __ext4_read_bh fs/ext4/super.c:205 [inline] ext4_read_bh_nowait+0x15a/0x240 fs/ext4/super.c:217 ext4_read_bh_lock+0xac/0xd0 fs/ext4/super.c:242 ext4_bread_batch+0x268/0x500 fs/ext4/inode.c:958 __ext4_find_entry+0x448/0x10f0 fs/ext4/namei.c:1671 ext4_lookup_entry fs/ext4/namei.c:1774 [inline] ext4_lookup.part.0+0x359/0x6f0 fs/ext4/namei.c:1842 ext4_lookup+0x72/0x90 fs/ext4/namei.c:1839 __lookup_slow+0x257/0x480 fs/namei.c:1696 lookup_slow fs/namei.c:1713 [inline] walk_component+0x454/0x5c0 fs/namei.c:2004 link_path_walk.part.0+0x773/0xda0 fs/namei.c:2331 link_path_walk fs/namei.c:3826 [inline] path_openat+0x1b9/0x520 fs/namei.c:3826 do_filp_open+0x1b7/0x400 fs/namei.c:3857 do_sys_openat2+0x5dc/0x6e0 fs/open.c:1428 do_sys_open fs/open.c:1443 [inline] __do_sys_openat fs/open.c:1459 [inline] __se_sys_openat fs/open.c:1454 [inline] __x64_sys_openat+0x148/0x200 fs/open.c:1454 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_6 ---truncado---"
          }
        ],
        "id": "CVE-2025-21631",
        "lastModified": "2026-06-17T08:43:53.313",
        "metrics": {
          "cvssMetricV31": [
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              "impactScore": 5.9,
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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          "ssvcV203": [
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        "references": [
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          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
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              {
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                "value": "CWE-416"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
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            ],
            "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-23T19:52:14+00:00",
      "cve": "CVE-2025-21631",
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      "initial_release_date": "2025-01-19T00:00:00+00:00",
      "product_status:fixed": "303",
      "product_status:known_affected": "98",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: block, bfq: fix waker_bfqq UAF after bfq_split_bfqq()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21631.json",
      "version": "3"
    },
    "suse_vex": {
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      "current_release_date": "2026-09-01T13:53:15Z",
      "cve": "CVE-2025-21631",
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      "product_status:known_affected": "410",
      "product_status:known_not_affected": "428",
      "product_status:recommended": "398",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-21631",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-21631.json",
      "version": "52"
    },
    "vulnrichment": {
      "containers": {
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            "references": [
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            ],
            "title": "CVE Program Container"
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          {
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                  "version": "3.1"
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              },
              {
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                  "content": {
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                      {
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            ],
            "problemTypes": [
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                  {
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                    "description": "CWE-416 Use After Free",
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                    "type": "CWE"
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              }
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              "shortName": "CISA-ADP"
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            "title": "CISA ADP Vulnrichment"
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        "cna": {
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              "product": "Linux",
              "programFiles": [
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          "cpeApplicability": [
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                    {
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                    {
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            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblock, bfq: fix waker_bfqq UAF after bfq_split_bfqq()\n\nOur syzkaller report a following UAF for v6.6:\n\nBUG: KASAN: slab-use-after-free in bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958\nRead of size 8 at addr ffff8881b57147d8 by task fsstress/232726\n\nCPU: 2 PID: 232726 Comm: fsstress Not tainted 6.6.0-g3629d1885222 #39\nCall Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:88 [inline]\n dump_stack_lvl+0x91/0xf0 lib/dump_stack.c:106\n print_address_description.constprop.0+0x66/0x300 mm/kasan/report.c:364\n print_report+0x3e/0x70 mm/kasan/report.c:475\n kasan_report+0xb8/0xf0 mm/kasan/report.c:588\n hlist_add_head include/linux/list.h:1023 [inline]\n bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958\n bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271\n bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323\n blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660\n blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143\n __submit_bio+0xa0/0x6b0 block/blk-core.c:639\n __submit_bio_noacct_mq block/blk-core.c:718 [inline]\n submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747\n submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847\n __ext4_read_bh fs/ext4/super.c:205 [inline]\n ext4_read_bh+0x15e/0x2e0 fs/ext4/super.c:230\n __read_extent_tree_block+0x304/0x6f0 fs/ext4/extents.c:567\n ext4_find_extent+0x479/0xd20 fs/ext4/extents.c:947\n ext4_ext_map_blocks+0x1a3/0x2680 fs/ext4/extents.c:4182\n ext4_map_blocks+0x929/0x15a0 fs/ext4/inode.c:660\n ext4_iomap_begin_report+0x298/0x480 fs/ext4/inode.c:3569\n iomap_iter+0x3dd/0x1010 fs/iomap/iter.c:91\n iomap_fiemap+0x1f4/0x360 fs/iomap/fiemap.c:80\n ext4_fiemap+0x181/0x210 fs/ext4/extents.c:5051\n ioctl_fiemap.isra.0+0x1b4/0x290 fs/ioctl.c:220\n do_vfs_ioctl+0x31c/0x11a0 fs/ioctl.c:811\n __do_sys_ioctl fs/ioctl.c:869 [inline]\n __se_sys_ioctl+0xae/0x190 fs/ioctl.c:857\n do_syscall_x64 arch/x86/entry/common.c:51 [inline]\n do_syscall_64+0x70/0x120 arch/x86/entry/common.c:81\n entry_SYSCALL_64_after_hwframe+0x78/0xe2\n\nAllocated by task 232719:\n kasan_save_stack+0x22/0x50 mm/kasan/common.c:45\n kasan_set_track+0x25/0x30 mm/kasan/common.c:52\n __kasan_slab_alloc+0x87/0x90 mm/kasan/common.c:328\n kasan_slab_alloc include/linux/kasan.h:188 [inline]\n slab_post_alloc_hook mm/slab.h:768 [inline]\n slab_alloc_node mm/slub.c:3492 [inline]\n kmem_cache_alloc_node+0x1b8/0x6f0 mm/slub.c:3537\n bfq_get_queue+0x215/0x1f00 block/bfq-iosched.c:5869\n bfq_get_bfqq_handle_split+0x167/0x5f0 block/bfq-iosched.c:6776\n bfq_init_rq+0x13a4/0x17a0 block/bfq-iosched.c:6938\n bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271\n bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323\n blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660\n blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143\n __submit_bio+0xa0/0x6b0 block/blk-core.c:639\n __submit_bio_noacct_mq block/blk-core.c:718 [inline]\n submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747\n submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847\n __ext4_read_bh fs/ext4/super.c:205 [inline]\n ext4_read_bh_nowait+0x15a/0x240 fs/ext4/super.c:217\n ext4_read_bh_lock+0xac/0xd0 fs/ext4/super.c:242\n ext4_bread_batch+0x268/0x500 fs/ext4/inode.c:958\n __ext4_find_entry+0x448/0x10f0 fs/ext4/namei.c:1671\n ext4_lookup_entry fs/ext4/namei.c:1774 [inline]\n ext4_lookup.part.0+0x359/0x6f0 fs/ext4/namei.c:1842\n ext4_lookup+0x72/0x90 fs/ext4/namei.c:1839\n __lookup_slow+0x257/0x480 fs/namei.c:1696\n lookup_slow fs/namei.c:1713 [inline]\n walk_component+0x454/0x5c0 fs/namei.c:2004\n link_path_walk.part.0+0x773/0xda0 fs/namei.c:2331\n link_path_walk fs/namei.c:3826 [inline]\n path_openat+0x1b9/0x520 fs/namei.c:3826\n do_filp_open+0x1b7/0x400 fs/namei.c:3857\n do_sys_openat2+0x5dc/0x6e0 fs/open.c:1428\n do_sys_open fs/open.c:1443 [inline]\n __do_sys_openat fs/open.c:1459 [inline]\n __se_sys_openat fs/open.c:1454 [inline]\n __x64_sys_openat+0x148/0x200 fs/open.c:1454\n do_syscall_x64 arch/x86/entry/common.c:51 [inline]\n do_syscall_6\n---truncated---"
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:L - The vulnerable code is the BFQ I/O scheduler, reached through ordinary local syscalls (read/write/openat/ioctl) that submit block I/O via submit_bio() \u2192 blk_mq_submit_bio() \u2192 bfq_insert_requests() \u2192 bfq_init_rq(). No remote data is processed by this path.\nAC:L - The free (bfq_split_bfqq \u2192 bfq_release_process_ref \u2192 bfq_put_queue) and the use (hlist_add_head on the dangling waker_bfqq) occur in the same task within a single bfq_init_rq() call, so there is no race window to win; the attacker fully controls the preconditions (cooperating-queue merge, split_coop, and waker detection) by spawning their own processes with a chosen I/O pattern, and syzkaller hit it with plain fsstress.\nPR:L - Any unprivileged local user can trigger this with normal file I/O on a BFQ-scheduled device \u2014 there is no capability check anywhere along bfq_prepare_request/bfq_init_rq/bfq_get_bfqq_handle_split, and it is reachable from inside containers and restricted sandboxes.\nUI:N - The attacker\u0027s own I/O workload creates the queue-merge, split, and waker-detection state; no action by any other user or victim process is needed.\nS:U - The use-after-free corrupts kernel heap memory within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The freed bfq_queue is reallocated from the bfq_pool slab and its contents are read back (h-\u003efirst in hlist_add_head, and later bfqq-\u003ewaker_bfqq-\u003enext_rq / budget reads in bfq_select_queue), giving a controllable kernel-memory disclosure primitive that can leak heap pointers and defeat KASLR.\nI:H - hlist_add_head() on the freed object performs WRITE_ONCE(first-\u003epprev, \u0026n-\u003enext), writing a live kernel heap pointer to an address taken from attacker-reclaimed memory \u2014 an arbitrary-write primitive \u2014 plus writes into the freed object itself, which is exploitable for privilege escalation.\nA:H - The use-after-free reliably corrupts the bfq_pool slab and the scheduler\u0027s woken_list, producing KASAN splats, list corruption, and kernel panics in the block layer, halting the system."
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-05T11:53:16.126Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/f587c1ac68956c4703857d650d9b1cd7bb2ac4d7"
            },
            {
              "url": "https://git.kernel.org/stable/c/2550149fcdf2934155ff625d76ad4e3d4b25bbc6"
            },
            {
              "url": "https://git.kernel.org/stable/c/be3eed59ac01f429ac10aaa46e26f653bcf581ab"
            },
            {
              "url": "https://git.kernel.org/stable/c/bc2aeb35ff167e0c6b0cedf0c96a5c41e6cba1ed"
            },
            {
              "url": "https://git.kernel.org/stable/c/fcede1f0a043ccefe9bc6ad57f12718e42f63f1d"
            }
          ],
          "title": "block, bfq: fix waker_bfqq UAF after bfq_split_bfqq()",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2025-21631",
        "datePublished": "2025-01-19T10:17:49.439Z",
        "dateReserved": "2024-12-29T08:45:45.726Z",
        "dateUpdated": "2026-08-05T11:53:16.126Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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