6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Xinyu Zhang <xizhang@xxxxxxxxxxxxxxx>
[ Upstream commit 2ff949441802a8d076d9013c7761f63e8ae5a9bd ]
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: Sasha Levin <sashal@xxxxxxxxxx>
---
block/blk-map.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/block/blk-map.c b/block/blk-map.c
index 71210cdb34426..0aadbaf7a9ddd 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -600,9 +600,7 @@ static int blk_rq_map_user_bvec(struct request *rq, const struct iov_iter *iter)
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;
--
2.43.0
