[dm-devel] [RFC PATCH] bio-integrity: Fix regression if profile verify_fn is NULL

[Thorsten Leemhuis]

TWIMC: This issue is tracked in the regression reports for Linux 4.13
(http://bit.ly/lnxregrep413 ) with this id:

Linux-Regression-ID: lr#35498d

Please include this line in the comment section of patches that are
supposed to fix the issue. Please also mention the string once in other
mailinglist threads or different bug tracking entries if you or someone
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here: http://bit.ly/lnxregtrackid

Thx for your help. And thx to Milan for pointing me to this regression.
 Ciao, Thorsten

On 02.08.2017 14:27, Milan Broz wrote:
> In dm-integrity target we register integrity profile that have
> both generate_fn and verify_fn callbacks set to NULL.
> 
> This is used if dm-integrity is stacked under a dm-crypt device
> for authenticated encryption (integrity payload contains authentication
> tag and IV seed).
> 
> In this case the verification is done through own crypto API
> processing inside dm-crypt; integrity profile is only holder
> of these data. (And memory is owned by dm-crypt as well.)
> 
> After the commit (and previous changes)
>   Commit 7c20f11680a441df09de7235206f70115fbf6290
>   Author: Christoph Hellwig <hch at lst.de>
>   Date:   Mon Jul 3 16:58:43 2017 -0600
> 
>     bio-integrity: stop abusing bi_end_io
> 
> we get this crash:
> 
> : BUG: unable to handle kernel NULL pointer dereference at   (null)
> : IP:   (null)
> : *pde = 00000000
> ...
> :
> : Workqueue: kintegrityd bio_integrity_verify_fn
> : task: f48ae180 task.stack: f4b5c000
> : EIP:   (null)
> : EFLAGS: 00210286 CPU: 0
> : EAX: f4b5debc EBX: 00001000 ECX: 00000001 EDX: 00000000
> : ESI: 00001000 EDI: ed25f000 EBP: f4b5dee8 ESP: f4b5dea4
> :  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
> : CR0: 80050033 CR2: 00000000 CR3: 32823000 CR4: 001406d0
> : Call Trace:
> :  ? bio_integrity_process+0xe3/0x1e0
> :  bio_integrity_verify_fn+0xea/0x150
> :  process_one_work+0x1c7/0x5c0
> :  worker_thread+0x39/0x380
> :  kthread+0xd6/0x110
> :  ? process_one_work+0x5c0/0x5c0
> :  ? kthread_worker_fn+0x100/0x100
> :  ? kthread_worker_fn+0x100/0x100
> :  ret_from_fork+0x19/0x24
> : Code:  Bad EIP value.
> : EIP:   (null) SS:ESP: 0068:f4b5dea4
> : CR2: 0000000000000000
> 
> Patch just skip the whole verify workqueue if verify_fn is set to NULL.
> 
> Signed-off-by: Milan Broz <gmazyland at gmail.com>
> ---
>  block/bio-integrity.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/block/bio-integrity.c b/block/bio-integrity.c
> index 83e92beb3c9f..b9d1580bfc13 100644
> --- a/block/bio-integrity.c
> +++ b/block/bio-integrity.c
> @@ -387,7 +387,9 @@ static void bio_integrity_verify_fn(struct work_struct *work)
>   */
>  bool __bio_integrity_endio(struct bio *bio)
>  {
> -	if (bio_op(bio) == REQ_OP_READ && !bio->bi_status) {
> +	struct blk_integrity *bi = bdev_get_integrity(bio->bi_bdev);
> +
> +	if (bi->profile->verify_fn && bio_op(bio) == REQ_OP_READ && !bio->bi_status) {
>  		struct bio_integrity_payload *bip = bio_integrity(bio);
>  
>  		INIT_WORK(&bip->bip_work, bio_integrity_verify_fn);
>