[PATCH] block: check bio split for unaligned bvec

[PATCH] block: check bio split for unaligned bvec

[Keith Busch]

From: Keith Busch <kbusch@kernel.org>

Offsets and lengths need to be validated against the dma alignment. This
check was skipped for sufficiently a small bio with a single bvec, which
may allow an invalid request dispatched to the driver. Force the
validation for an unaligned bvec by forcing the bio split path that
handles this condition.

Fixes: 7eac33186957 ("iomap: simplify direct io validity check")
Fixes: 5ff3f74e145a ("block: simplify direct io validity check")
Reported-by: Carlos Maiolino <cem@kernel.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 block/blk.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/blk.h b/block/blk.h
index 1a2d9101bba04..004048fa0c5a8 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -404,6 +404,8 @@ static inline bool bio_may_need_split(struct bio *bio,
 	bv = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
 	if (bio->bi_iter.bi_size > bv->bv_len - bio->bi_iter.bi_bvec_done)
 		return true;
+	if ((bv->bv_offset | bv->bv_len) & lim->dma_alignment)
+		return true;
 	return bv->bv_len + bv->bv_offset > lim->max_fast_segment_size;
 }
 
-- 
2.52.0

Re: [PATCH] block: check bio split for unaligned bvec

[Jens Axboe]

On Fri, 12 Jun 2026 15:32:04 -0700, Keith Busch wrote:
> Offsets and lengths need to be validated against the dma alignment. This
> check was skipped for sufficiently a small bio with a single bvec, which
> may allow an invalid request dispatched to the driver. Force the
> validation for an unaligned bvec by forcing the bio split path that
> handles this condition.
> 
> 
> [...]

Applied, thanks!

[1/1] block: check bio split for unaligned bvec
      commit: 9b0c3673c88588d613d8f09f5931b2b466c6a83d

Best regards,
-- 
Jens Axboe

Re: [PATCH] block: check bio split for unaligned bvec

[Carlos Maiolino]

On Fri, Jun 12, 2026 at 03:32:04PM -0700, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> Offsets and lengths need to be validated against the dma alignment. This
> check was skipped for sufficiently a small bio with a single bvec, which
> may allow an invalid request dispatched to the driver. Force the
> validation for an unaligned bvec by forcing the bio split path that
> handles this condition.
> 
> Fixes: 7eac33186957 ("iomap: simplify direct io validity check")
> Fixes: 5ff3f74e145a ("block: simplify direct io validity check")
> Reported-by: Carlos Maiolino <cem@kernel.org>
> Signed-off-by: Keith Busch <kbusch@kernel.org>

Jens was quick enough but if needed anyway, I've tested this locally,
so:

Tested-by: Carlos Maiolino <cem@kernel.org>
Reviewed-by: Carlos Maiolino <cem@kernel.org>

> ---
>  block/blk.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/block/blk.h b/block/blk.h
> index 1a2d9101bba04..004048fa0c5a8 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -404,6 +404,8 @@ static inline bool bio_may_need_split(struct bio *bio,
>  	bv = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
>  	if (bio->bi_iter.bi_size > bv->bv_len - bio->bi_iter.bi_bvec_done)
>  		return true;
> +	if ((bv->bv_offset | bv->bv_len) & lim->dma_alignment)
> +		return true;
>  	return bv->bv_len + bv->bv_offset > lim->max_fast_segment_size;
>  }
>  
> -- 
> 2.52.0
> 

Re: [PATCH] block: check bio split for unaligned bvec

[Christoph Hellwig]

On Fri, Jun 12, 2026 at 03:32:04PM -0700, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> Offsets and lengths need to be validated against the dma alignment. This
> check was skipped for sufficiently a small bio with a single bvec, which
> may allow an invalid request dispatched to the driver. Force the
> validation for an unaligned bvec by forcing the bio split path that
> handles this condition.

This fix itself looks good, but we'll also need something similar
for bio-based drivers that never call into the splitting helper.