Message-ID: <68843449.a00a0220.b12ec.0000.GAE@google.com>
Date: Fri, 25 Jul 2025 18:50:01 -0700
From: syzbot <syzbot+a6ffe86390c8a6afc818@...kaller.appspotmail.com>
To: eadavis@...com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [rdma?] KASAN: slab-use-after-free Read in ucma_create_uevent

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Write in ucma_create_uevent

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_inc_not_zero include/linux/atomic/atomic-instrumented.h:1536 [inline]
BUG: KASAN: slab-use-after-free in ucma_get_mc drivers/infiniband/core/ucma.c:263 [inline]
BUG: KASAN: slab-use-after-free in ucma_create_uevent+0x8d1/0xd70 drivers/infiniband/core/ucma.c:287
Write of size 4 at addr ffff88802a9566b0 by task kworker/u32:5/1140

CPU: 2 UID: 0 PID: 1140 Comm: kworker/u32:5 Not tainted 6.16.0-rc7-syzkaller-g5f33ebd2018c-dirty #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: rdma_cm cma_iboe_join_work_handler
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xcd/0x630 mm/kasan/report.c:482
 kasan_report+0xe0/0x110 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:183 [inline]
 kasan_check_range+0x100/0x1b0 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_inc_not_zero include/linux/atomic/atomic-instrumented.h:1536 [inline]
 ucma_get_mc drivers/infiniband/core/ucma.c:263 [inline]
 ucma_create_uevent+0x8d1/0xd70 drivers/infiniband/core/ucma.c:287
 ucma_event_handler+0x102/0x940 drivers/infiniband/core/ucma.c:366
 cma_cm_event_handler+0x97/0x300 drivers/infiniband/core/cma.c:2173
 cma_iboe_join_work_handler+0xca/0x170 drivers/infiniband/core/cma.c:3008
 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6548:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 ucma_process_join+0x233/0xb90 drivers/infiniband/core/ucma.c:1480
 ucma_join_multicast+0xe8/0x160 drivers/infiniband/core/ucma.c:1575
 ucma_write+0x1fb/0x330 drivers/infiniband/core/ucma.c:1756
 vfs_write+0x29d/0x1150 fs/read_write.c:684
 ksys_write+0x1f8/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6548:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2381 [inline]
 slab_free mm/slub.c:4643 [inline]
 kfree+0x2b4/0x4d0 mm/slub.c:4842
 ucma_put_mc drivers/infiniband/core/ucma.c:269 [inline]
 ucma_put_mc drivers/infiniband/core/ucma.c:266 [inline]
 ucma_process_join+0x763/0xb90 drivers/infiniband/core/ucma.c:1534
 ucma_join_multicast+0xe8/0x160 drivers/infiniband/core/ucma.c:1575
 ucma_write+0x1fb/0x330 drivers/infiniband/core/ucma.c:1756
 vfs_write+0x29d/0x1150 fs/read_write.c:684
 ksys_write+0x1f8/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802a956600
 which belongs to the cache kmalloc-192 of size 192
The buggy address is located 176 bytes inside of
 freed 192-byte region [ffff88802a956600, ffff88802a9566c0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2a956
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801b8423c0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x252800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP|__GFP_THISNODE), pid 6445, tgid 6445 (syz-executor), ts 92358145050, free_ts 92277395639
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x1321/0x3890 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:4959
 alloc_slab_page mm/slub.c:2453 [inline]
 allocate_slab mm/slub.c:2619 [inline]
 new_slab+0x94/0x330 mm/slub.c:2673
 ___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
 __slab_alloc_node mm/slub.c:4024 [inline]
 slab_alloc_node mm/slub.c:4185 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_node_noprof+0x2ed/0x500 mm/slub.c:4334
 kmalloc_array_node_noprof include/linux/slab.h:1020 [inline]
 alloc_slab_obj_exts+0x41/0xa0 mm/slub.c:1992
 account_slab mm/slub.c:2578 [inline]
 allocate_slab mm/slub.c:2638 [inline]
 new_slab+0x283/0x330 mm/slub.c:2673
 ___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
 __slab_alloc_node mm/slub.c:4024 [inline]
 slab_alloc_node mm/slub.c:4185 [inline]
 kmem_cache_alloc_lru_noprof+0xf4/0x3b0 mm/slub.c:4216
 sock_alloc_inode+0x25/0x1c0 net/socket.c:309
 alloc_inode+0x61/0x240 fs/inode.c:346
 new_inode_pseudo include/linux/fs.h:3364 [inline]
 sock_alloc+0x40/0x280 net/socket.c:622
 __sock_create+0xc1/0x8d0 net/socket.c:1505
page last free pid 23 tgid 23 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 __free_frozen_pages+0x7fe/0x1180 mm/page_alloc.c:2706
 pagetable_free include/linux/mm.h:2884 [inline]
 pagetable_dtor_free include/linux/mm.h:2982 [inline]
 __tlb_remove_table include/asm-generic/tlb.h:220 [inline]
 __tlb_remove_table_free mm/mmu_gather.c:227 [inline]
 tlb_remove_table_rcu+0x116/0x1a0 mm/mmu_gather.c:290
 rcu_do_batch kernel/rcu/tree.c:2576 [inline]
 rcu_core+0x79c/0x14e0 kernel/rcu/tree.c:2832
 handle_softirqs+0x219/0x8e0 kernel/softirq.c:579
 run_ksoftirqd kernel/softirq.c:968 [inline]
 run_ksoftirqd+0x3a/0x60 kernel/softirq.c:960
 smpboot_thread_fn+0x3f4/0xae0 kernel/smpboot.c:164
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff88802a956580: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
 ffff88802a956600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802a956680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                                     ^
 ffff88802a956700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802a956780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


Tested on:

commit:         5f33ebd2 Merge tag 'drm-fixes-2025-07-26' of https://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17ea88a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c445d2891161cc81
dashboard link: https://syzkaller.appspot.com/bug?extid=a6ffe86390c8a6afc818
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=12100782580000

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