[PATCH] block: bio: ensure newly added bio flags don't override BVEC_POOL_IDX

[PATCH] block: bio: ensure newly added bio flags don't override BVEC_POOL_IDX

[Johannes Thumshirn]

With the introduction of BIO_NO_PAGE_REF we've used up all available bits
in bio::bi_flags.

Convert the defines of the flags to an enum and add a BUILD_BUG_ON() call
to make sure no-one adds a new one and thus overrides the BVEC_POOL_IDX
causing crashes.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>

---
This used to be part of my bio patchset but as it's a) not clear why we
end up calling bio_put() on the on-stack bio and b) the needed prep patch
for the fix introduces a regression, I've decided to sent this patch out
as it's valid on it's own.

I dropped Hannes' and Christoph's R-b though, as the context changed.
---
 block/bio.c               |  3 +++
 include/linux/blk_types.h | 29 ++++++++++++++++-------------
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 8d516d508ae3..c2592c5d70b9 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -2218,6 +2218,9 @@ static int __init init_bio(void)
 	bio_slab_nr = 0;
 	bio_slabs = kcalloc(bio_slab_max, sizeof(struct bio_slab),
 			    GFP_KERNEL);
+
+	BUILD_BUG_ON(BIO_FLAG_LAST > BVEC_POOL_OFFSET);
+
 	if (!bio_slabs)
 		panic("bio: can't allocate bios\n");
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 791fee35df88..be418275763c 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -215,21 +215,24 @@ struct bio {
 /*
  * bio flags
  */
-#define BIO_NO_PAGE_REF	0	/* don't put release vec pages */
-#define BIO_SEG_VALID	1	/* bi_phys_segments valid */
-#define BIO_CLONED	2	/* doesn't own data */
-#define BIO_BOUNCED	3	/* bio is a bounce bio */
-#define BIO_USER_MAPPED 4	/* contains user pages */
-#define BIO_NULL_MAPPED 5	/* contains invalid user pages */
-#define BIO_QUIET	6	/* Make BIO Quiet */
-#define BIO_CHAIN	7	/* chained bio, ->bi_remaining in effect */
-#define BIO_REFFED	8	/* bio has elevated ->bi_cnt */
-#define BIO_THROTTLED	9	/* This bio has already been subjected to
+enum {
+	BIO_NO_PAGE_REF,	/* don't put release vec pages */
+	BIO_SEG_VALID,		/* bi_phys_segments valid */
+	BIO_CLONED,		/* doesn't own data */
+	BIO_BOUNCED,		/* bio is a bounce bio */
+	BIO_USER_MAPPED,	/* contains user pages */
+	BIO_NULL_MAPPED,	/* contains invalid user pages */
+	BIO_QUIET,		/* Make BIO Quiet */
+	BIO_CHAIN,		/* chained bio, ->bi_remaining in effect */
+	BIO_REFFED,		/* bio has elevated ->bi_cnt */
+	BIO_THROTTLED,		/* This bio has already been subjected to
 				 * throttling rules. Don't do it again. */
-#define BIO_TRACE_COMPLETION 10	/* bio_endio() should trace the final completion
+	BIO_TRACE_COMPLETION,	/* bio_endio() should trace the final completion
 				 * of this bio. */
-#define BIO_QUEUE_ENTERED 11	/* can use blk_queue_enter_live() */
-#define BIO_TRACKED 12		/* set if bio goes through the rq_qos path */
+	BIO_QUEUE_ENTERED,	/* can use blk_queue_enter_live() */
+	BIO_TRACKED,		/* set if bio goes through the rq_qos path */
+	BIO_FLAG_LAST
+};
 
 /* See BVEC_POOL_OFFSET below before adding new flags */
 
-- 
2.16.4

Re: [PATCH] block: bio: ensure newly added bio flags don't override BVEC_POOL_IDX

[Ming Lei]

On Wed, Apr 3, 2019 at 5:16 PM Johannes Thumshirn <jthumshirn@suse.de> wrote:
>
> With the introduction of BIO_NO_PAGE_REF we've used up all available bits
> in bio::bi_flags.
>
> Convert the defines of the flags to an enum and add a BUILD_BUG_ON() call
> to make sure no-one adds a new one and thus overrides the BVEC_POOL_IDX
> causing crashes.
>
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
>
> ---
> This used to be part of my bio patchset but as it's a) not clear why we
> end up calling bio_put() on the on-stack bio and b) the needed prep patch
> for the fix introduces a regression, I've decided to sent this patch out
> as it's valid on it's own.
>
> I dropped Hannes' and Christoph's R-b though, as the context changed.
> ---
>  block/bio.c               |  3 +++
>  include/linux/blk_types.h | 29 ++++++++++++++++-------------
>  2 files changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 8d516d508ae3..c2592c5d70b9 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -2218,6 +2218,9 @@ static int __init init_bio(void)
>         bio_slab_nr = 0;
>         bio_slabs = kcalloc(bio_slab_max, sizeof(struct bio_slab),
>                             GFP_KERNEL);
> +
> +       BUILD_BUG_ON(BIO_FLAG_LAST > BVEC_POOL_OFFSET);
> +
>         if (!bio_slabs)
>                 panic("bio: can't allocate bios\n");
>
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 791fee35df88..be418275763c 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -215,21 +215,24 @@ struct bio {
>  /*
>   * bio flags
>   */
> -#define BIO_NO_PAGE_REF        0       /* don't put release vec pages */
> -#define BIO_SEG_VALID  1       /* bi_phys_segments valid */
> -#define BIO_CLONED     2       /* doesn't own data */
> -#define BIO_BOUNCED    3       /* bio is a bounce bio */
> -#define BIO_USER_MAPPED 4      /* contains user pages */
> -#define BIO_NULL_MAPPED 5      /* contains invalid user pages */
> -#define BIO_QUIET      6       /* Make BIO Quiet */
> -#define BIO_CHAIN      7       /* chained bio, ->bi_remaining in effect */
> -#define BIO_REFFED     8       /* bio has elevated ->bi_cnt */
> -#define BIO_THROTTLED  9       /* This bio has already been subjected to
> +enum {
> +       BIO_NO_PAGE_REF,        /* don't put release vec pages */
> +       BIO_SEG_VALID,          /* bi_phys_segments valid */
> +       BIO_CLONED,             /* doesn't own data */
> +       BIO_BOUNCED,            /* bio is a bounce bio */
> +       BIO_USER_MAPPED,        /* contains user pages */
> +       BIO_NULL_MAPPED,        /* contains invalid user pages */
> +       BIO_QUIET,              /* Make BIO Quiet */
> +       BIO_CHAIN,              /* chained bio, ->bi_remaining in effect */
> +       BIO_REFFED,             /* bio has elevated ->bi_cnt */
> +       BIO_THROTTLED,          /* This bio has already been subjected to
>                                  * throttling rules. Don't do it again. */
> -#define BIO_TRACE_COMPLETION 10        /* bio_endio() should trace the final completion
> +       BIO_TRACE_COMPLETION,   /* bio_endio() should trace the final completion
>                                  * of this bio. */
> -#define BIO_QUEUE_ENTERED 11   /* can use blk_queue_enter_live() */
> -#define BIO_TRACKED 12         /* set if bio goes through the rq_qos path */
> +       BIO_QUEUE_ENTERED,      /* can use blk_queue_enter_live() */
> +       BIO_TRACKED,            /* set if bio goes through the rq_qos path */
> +       BIO_FLAG_LAST
> +};
>
>  /* See BVEC_POOL_OFFSET below before adding new flags */

Looks fine,

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming Lei

Re: [PATCH] block: bio: ensure newly added bio flags don't override BVEC_POOL_IDX

[Hannes Reinecke]

On 4/3/19 11:15 AM, Johannes Thumshirn wrote:
> With the introduction of BIO_NO_PAGE_REF we've used up all available bits
> in bio::bi_flags.
> 
> Convert the defines of the flags to an enum and add a BUILD_BUG_ON() call
> to make sure no-one adds a new one and thus overrides the BVEC_POOL_IDX
> causing crashes.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
> 
> ---
> This used to be part of my bio patchset but as it's a) not clear why we
> end up calling bio_put() on the on-stack bio and b) the needed prep patch
> for the fix introduces a regression, I've decided to sent this patch out
> as it's valid on it's own.
> 
> I dropped Hannes' and Christoph's R-b though, as the context changed.
> ---
>   block/bio.c               |  3 +++
>   include/linux/blk_types.h | 29 ++++++++++++++++-------------
>   2 files changed, 19 insertions(+), 13 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke            Teamlead Storage & Networking
hare@suse.de                              +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)

Re: [PATCH] block: bio: ensure newly added bio flags don't override BVEC_POOL_IDX

[Bart Van Assche]

On Wed, 2019-04-03 at 11:15 +0200, Johannes Thumshirn wrote:
> With the introduction of BIO_NO_PAGE_REF we've used up all available bits
> in bio::bi_flags.
> 
> Convert the defines of the flags to an enum and add a BUILD_BUG_ON() call
> to make sure no-one adds a new one and thus overrides the BVEC_POOL_IDX
> causing crashes.

Reviewed-by: Bart Van Assche <bvanassche@acm.org>

Re: [PATCH] block: bio: ensure newly added bio flags don't override BVEC_POOL_IDX

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH] block: bio: ensure newly added bio flags don't override BVEC_POOL_IDX

[Jens Axboe]

On 4/3/19 3:15 AM, Johannes Thumshirn wrote:
> With the introduction of BIO_NO_PAGE_REF we've used up all available bits
> in bio::bi_flags.
> 
> Convert the defines of the flags to an enum and add a BUILD_BUG_ON() call
> to make sure no-one adds a new one and thus overrides the BVEC_POOL_IDX
> causing crashes.

Applied for 5.2, thanks.

-- 
Jens Axboe