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Dawei Feng d1fef92e41 rbd: fix null-ptr-deref when device_add_disk() fails 
do_rbd_add() publishes the device with device_add() before calling
device_add_disk(). If device_add_disk() fails after device_add()
succeeds, the error path calls rbd_free_disk() directly and then later
falls through to rbd_dev_device_release(), which calls rbd_free_disk()
again. This double teardown can leave blk-mq cleanup operating on
invalid state and trigger a null-ptr-deref in
__blk_mq_free_map_and_rqs(), reached from blk_mq_free_tag_set().

Fix this by following the normal remove ordering: call device_del()
before rbd_dev_device_release() when device_add_disk() fails after
device_add(). That keeps the teardown sequence consistent and avoids
re-entering disk cleanup through the wrong path.

The bug was first flagged by an experimental analysis tool we are
developing for kernel memory-management bugs while analyzing
v6.13-rc1. The tool is still under development and is not yet publicly
available.

We reproduced the bug on v7.0 with a real Ceph backend and a QEMU x86_64
guest booted with KASAN and CONFIG_FAILSLAB enabled. The reproducer
confines failslab injections to the __add_disk() range and injects
fail-nth while mapping an RBD image through
/sys/bus/rbd/add_single_major.

On the unpatched kernel, fail-nth=4 reliably triggered the fault:

	Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
	KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
	CPU: 0 UID: 0 PID: 273 Comm: bash Not tainted 7.0.0-01247-gd60bc1401583 #6 PREEMPT(lazy)
	Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
	RIP: 0010:__blk_mq_free_map_and_rqs+0x8c/0x240
	Code: 00 00 48 8b 6b 60 41 89 f4 49 c1 e4 03 4c 01 e5 45 85 ed 0f 85 0a 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 e9 48 c1 e9 03 <80> 3c 01 00 0f 85 31 01 00 00 4c 8b 6d 00 4d 85 ed 0f 84 e2 00 00
	RSP: 0018:ff1100000ab0fac8 EFLAGS: 00000246
	RAX: dffffc0000000000 RBX: ff1100000c4806a0 RCX: 0000000000000000
	RDX: 0000000000000002 RSI: 0000000000000000 RDI: ff1100000c4806f4
	RBP: 0000000000000000 R08: 0000000000000001 R09: ffe21c000189001b
	R10: ff1100000c4800df R11: ff1100006cf37be0 R12: 0000000000000000
	R13: 0000000000000000 R14: ff1100000c480700 R15: ff1100000c480004
	FS:  00007f0fbe8fe740(0000) GS:ff110000e5851000(0000) knlGS:0000000000000000
	CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
	CR2: 00007fe53473b2e0 CR3: 0000000012eef000 CR4: 00000000007516f0
	PKRU: 55555554
	Call Trace:
	 <TASK>
	 blk_mq_free_tag_set+0x77/0x460
	 do_rbd_add+0x1446/0x2b80
	 ? __pfx_do_rbd_add+0x10/0x10
	 ? lock_acquire+0x18c/0x300
	 ? find_held_lock+0x2b/0x80
	 ? sysfs_file_kobj+0xb6/0x1b0
	 ? __pfx_sysfs_kf_write+0x10/0x10
	 kernfs_fop_write_iter+0x2f4/0x4a0
	 vfs_write+0x98e/0x1000
	 ? expand_files+0x51f/0x850
	 ? __pfx_vfs_write+0x10/0x10
	 ksys_write+0xf2/0x1d0
	 ? __pfx_ksys_write+0x10/0x10
	 do_syscall_64+0x115/0x690
	 entry_SYSCALL_64_after_hwframe+0x77/0x7f
	RIP: 0033:0x7f0fbea15907
	Code: 10 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
	RSP: 002b:00007ffe22346ea8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
	RAX: ffffffffffffffda RBX: 0000000000000058 RCX: 00007f0fbea15907
	RDX: 0000000000000058 RSI: 0000563ace6c0ef0 RDI: 0000000000000001
	RBP: 0000563ace6c0ef0 R08: 0000563ace6c0ef0 R09: 6b6435726d694141
	R10: 5250337279762f78 R11: 0000000000000246 R12: 0000000000000058
	R13: 00007f0fbeb1c780 R14: ff1100000c480700 R15: ff1100000c480004
	 </TASK>

With this fix applied, rerunning the reproducer over fail-nth=1..256
yields no KASAN reports.

[ idryomov: rename err_out_device_del -> err_out_device ]

Cc: stable@vger.kernel.org
Fixes: 27c97abc30 ("rbd: add add_disk() error handling")
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Signed-off-by: Dawei Feng <dawei.feng@seu.edu.cn>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
2026-04-22 01:40:23 +02:00
..
aoe Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
drbd block-7.0-20260227 2026-02-27 10:42:02 -08:00
mtip32xx block: switch ->getgeo() to struct gendisk 2025-08-13 02:59:29 -04:00
null_blk Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
rnbd Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
rnull configfs changes for v7.0 2026-02-12 14:01:38 -08:00
xen-blkback Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
zram zram: do not slot_free() written-back slots 2026-03-21 17:36:33 -07:00
amiflop.c block: switch ->getgeo() to struct gendisk 2025-08-13 02:59:29 -04:00
ataflop.c
brd.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
floppy.c array_size.h: add ARRAY_END() 2026-01-20 19:44:19 -08:00
Kconfig rbd: stop selecting CRC32, CRYPTO, and CRYPTO_AES 2025-12-10 11:50:54 +01:00
loop.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
Makefile rnull: move driver to separate directory 2025-09-02 05:23:56 -06:00
n64cart.c
nbd.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
ps3disk.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
ps3vram.c Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
rbd.c rbd: fix null-ptr-deref when device_add_disk() fails 2026-04-22 01:40:23 +02:00
rbd_types.h
sunvdc.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
swim.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
swim3.c
swim_asm.S
ublk_drv.c block-7.0-20260312 2026-03-13 10:13:06 -07:00
virtio_blk.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
xen-blkfront.c Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
z2ram.c Convert more 'alloc_obj' cases to default GFP_KERNEL arguments 2026-02-21 20:03:00 -08:00
zloop.c block-7.0-20260227 2026-02-27 10:42:02 -08:00