This is a note to let you know that I've just added the patch titled media: dvbdev: fix refcnt bug to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: media-dvbdev-fix-refcnt-bug.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 3a664569b71b0a52be5ffb9fb87cc4f83d29bd71 Mon Sep 17 00:00:00 2001 From: Lin Ma <linma@xxxxxxxxxx> Date: Mon, 28 Nov 2022 16:21:59 +0000 Subject: media: dvbdev: fix refcnt bug From: Lin Ma <linma@xxxxxxxxxx> commit 3a664569b71b0a52be5ffb9fb87cc4f83d29bd71 upstream. Previous commit initialize the dvbdev->ref before the template copy, which will overwrite the reference and cause refcnt bug. refcount_t: addition on 0; use-after-free. WARNING: CPU: 0 PID: 1 at lib/refcount.c:25 refcount_warn_saturate+0x17c/0x1f0 lib/refcount.c:25 Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc6-next-20221128-syzkaller #0 ... RIP: 0010:refcount_warn_saturate+0x17c/0x1f0 lib/refcount.c:25 RSP: 0000:ffffc900000678d0 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff88813ff58000 RSI: ffffffff81660e7c RDI: fffff5200000cf0c RBP: ffff888022a45010 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000080000000 R11: 0000000000000000 R12: 0000000000000001 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff88823ffff000 CR3: 000000000c48e000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> __refcount_add include/linux/refcount.h:199 [inline] __refcount_inc include/linux/refcount.h:250 [inline] refcount_inc include/linux/refcount.h:267 [inline] kref_get include/linux/kref.h:45 [inline] dvb_device_get drivers/media/dvb-core/dvbdev.c:585 [inline] dvb_register_device+0xe83/0x16e0 drivers/media/dvb-core/dvbdev.c:517 ... Just place the kref_init at correct position. Reported-by: syzbot+fce48a3dd3368645bd6c@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 0fc044b2b5e2 ("media: dvbdev: adopts refcnt to avoid UAF") Signed-off-by: Lin Ma <linma@xxxxxxxxxx> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/media/dvb-core/dvbdev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/media/dvb-core/dvbdev.c +++ b/drivers/media/dvb-core/dvbdev.c @@ -465,8 +465,8 @@ int dvb_register_device(struct dvb_adapt return -ENOMEM; } - kref_init(&dvbdev->ref); memcpy(dvbdev, template, sizeof(struct dvb_device)); + kref_init(&dvbdev->ref); dvbdev->type = type; dvbdev->id = id; dvbdev->adapter = adap; Patches currently in stable-queue which might be from linma@xxxxxxxxxx are queue-4.14/media-dvbdev-adopts-refcnt-to-avoid-uaf.patch queue-4.14/media-dvbdev-fix-refcnt-bug.patch