[PATCH 6.6 199/208] block: fix sanity checks in blk_rq_map_user_bvec

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6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xinyu Zhang <xizhang@xxxxxxxxxxxxxxx>

commit 2ff949441802a8d076d9013c7761f63e8ae5a9bd upstream.

blk_rq_map_user_bvec contains a check bytes + bv->bv_len > nr_iter which
causes unnecessary failures in NVMe passthrough I/O, reproducible as
follows:

- register a 2 page, page-aligned buffer against a ring
- use that buffer to do a 1 page io_uring NVMe passthrough read

The second (i = 1) iteration of the loop in blk_rq_map_user_bvec will
then have nr_iter == 1 page, bytes == 1 page, bv->bv_len == 1 page, so
the check bytes + bv->bv_len > nr_iter will succeed, causing the I/O to
fail. This failure is unnecessary, as when the check succeeds, it means
we've checked the entire buffer that will be used by the request - i.e.
blk_rq_map_user_bvec should complete successfully. Therefore, terminate
the loop early and return successfully when the check bytes + bv->bv_len
> nr_iter succeeds.

While we're at it, also remove the check that all segments in the bvec
are single-page. While this seems to be true for all users of the
function, it doesn't appear to be required anywhere downstream.

CC: stable@xxxxxxxxxxxxxxx
Signed-off-by: Xinyu Zhang <xizhang@xxxxxxxxxxxxxxx>
Co-developed-by: Uday Shankar <ushankar@xxxxxxxxxxxxxxx>
Signed-off-by: Uday Shankar <ushankar@xxxxxxxxxxxxxxx>
Fixes: 37987547932c ("block: extend functionality to map bvec iterator")
Link: https://lore.kernel.org/r/20241023211519.4177873-1-ushankar@xxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 block/blk-map.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -600,9 +600,7 @@ static int blk_rq_map_user_bvec(struct r
 		if (nsegs >= nr_segs || bytes > UINT_MAX - bv->bv_len)
 			goto put_bio;
 		if (bytes + bv->bv_len > nr_iter)
-			goto put_bio;
-		if (bv->bv_offset + bv->bv_len > PAGE_SIZE)
-			goto put_bio;
+			break;
 
 		nsegs++;
 		bytes += bv->bv_len;






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