linux-kernel - Re: [syzbot] [rdma?] KASAN: slab-use-after-free Read in ucma_create

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Message-ID: <686ddd12.050a0220.1ffab7.002e.GAE@google.com>
Date: Tue, 08 Jul 2025 20:08:02 -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 Read in ucma_create_uevent

==================================================================
BUG: KASAN: slab-use-after-free in ucma_create_uevent+0xadb/0xb30 drivers/infiniband/core/ucma.c:275
Read of size 8 at addr ffff888022289610 by task kworker/u32:2/46

CPU: 1 UID: 0 PID: 46 Comm: kworker/u32:2 Not tainted 6.16.0-rc5-syzkaller-g733923397fd9-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:408 [inline]
 print_report+0xcd/0x680 mm/kasan/report.c:521
 kasan_report+0xe0/0x110 mm/kasan/report.c:634
 ucma_create_uevent+0xadb/0xb30 drivers/infiniband/core/ucma.c:275
 ucma_event_handler+0x102/0x940 drivers/infiniband/core/ucma.c:351
 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+0x9cf/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
 kthread+0x3c5/0x780 kernel/kthread.c:464
 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6542:
 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+0x237/0xa30 drivers/infiniband/core/ucma.c:1465
 ucma_join_multicast+0xe8/0x160 drivers/infiniband/core/ucma.c:1557
 ucma_write+0x1fb/0x330 drivers/infiniband/core/ucma.c:1738
 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 6542:
 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_process_join+0x3b9/0xa30 drivers/infiniband/core/ucma.c:1516
 ucma_join_multicast+0xe8/0x160 drivers/infiniband/core/ucma.c:1557
 ucma_write+0x1fb/0x330 drivers/infiniband/core/ucma.c:1738
 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 ffff888022289600
 which belongs to the cache kmalloc-192 of size 192
The buggy address is located 16 bytes inside of
 freed 192-byte region [ffff888022289600, ffff8880222896c0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x22289
ksm flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801b8423c0 ffffea0000aeb500 dead000000000003
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 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1 (swapper/0), ts 3951737580, free_ts 0
 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_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2419
 alloc_slab_page mm/slub.c:2451 [inline]
 allocate_slab mm/slub.c:2619 [inline]
 new_slab+0x23b/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]
 __kmalloc_cache_noprof+0xfb/0x3e0 mm/slub.c:4354
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 __tty_alloc_driver drivers/tty/tty_io.c:3336 [inline]
 __tty_alloc_driver+0xbb/0x4a0 drivers/tty/tty_io.c:3326
 vty_init+0xdd/0x420 drivers/tty/vt/vt.c:3822
 tty_init+0x179/0x1c0 drivers/tty/tty_io.c:3649
 chr_dev_init+0xfb/0x170 drivers/char/mem.c:759
 do_one_initcall+0x120/0x6e0 init/main.c:1274
 do_initcall_level init/main.c:1336 [inline]
 do_initcalls init/main.c:1352 [inline]
 do_basic_setup init/main.c:1371 [inline]
 kernel_init_freeable+0x5c2/0x900 init/main.c:1584
 kernel_init+0x1c/0x2b0 init/main.c:1474
 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888022289500: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888022289580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888022289600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888022289680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff888022289700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


Tested on:

commit:         73392339 Merge tag 'pwm/for-6.16-rc6-fixes' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17363582580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8fa6c6703a4b2315
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=10bfca8c580000