6.1-stable review patch. If anyone has any objections, please let me know.
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From: Xinyu Zhang xizhang@purestorage.com
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@vger.kernel.org Signed-off-by: Xinyu Zhang xizhang@purestorage.com Co-developed-by: Uday Shankar ushankar@purestorage.com Signed-off-by: Uday Shankar ushankar@purestorage.com Fixes: 37987547932c ("block: extend functionality to map bvec iterator") Link: https://lore.kernel.org/r/20241023211519.4177873-1-ushankar@purestorage.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/blk-map.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
--- a/block/blk-map.c +++ b/block/blk-map.c @@ -597,9 +597,7 @@ 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;