From: Jens Axboe <axboe@kernel.dk>
Date: Wed, 16 Apr 2025 22:48:26 +0000 (-0600)
Subject: io_uring/rsrc: ensure segments counts are correct on kbuf buffers
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=b419bed4f0a62c65a57dd495185821dd56bc435c;p=nvme.git

io_uring/rsrc: ensure segments counts are correct on kbuf buffers

kbuf imports have the front offset adjusted and segments removed, but
the tail segments are still included in the segment count that gets
passed in the iov_iter. As the segments aren't necessarily all the
same size, move importing to a separate helper and iterate the
mapped length to get an exact count.

Reviewed-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 0c6d7e7415c8..f80a77c4973f 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1032,6 +1032,26 @@ static int validate_fixed_range(u64 buf_addr, size_t len,
 	return 0;
 }
 
+static int io_import_kbuf(int ddir, struct iov_iter *iter,
+			  struct io_mapped_ubuf *imu, size_t len, size_t offset)
+{
+	size_t count = len + offset;
+
+	iov_iter_bvec(iter, ddir, imu->bvec, imu->nr_bvecs, count);
+	iov_iter_advance(iter, offset);
+
+	if (count < imu->len) {
+		const struct bio_vec *bvec = iter->bvec;
+
+		while (len > bvec->bv_len) {
+			len -= bvec->bv_len;
+			bvec++;
+		}
+		iter->nr_segs = 1 + bvec - iter->bvec;
+	}
+	return 0;
+}
+
 static int io_import_fixed(int ddir, struct iov_iter *iter,
 			   struct io_mapped_ubuf *imu,
 			   u64 buf_addr, size_t len)
@@ -1052,11 +1072,8 @@ static int io_import_fixed(int ddir, struct iov_iter *iter,
 
 	offset = buf_addr - imu->ubuf;
 
-	if (imu->is_kbuf) {
-		iov_iter_bvec(iter, ddir, imu->bvec, imu->nr_bvecs, offset + len);
-		iov_iter_advance(iter, offset);
-		return 0;
-	}
+	if (imu->is_kbuf)
+		return io_import_kbuf(ddir, iter, imu, len, offset);
 
 	/*
 	 * Don't use iov_iter_advance() here, as it's really slow for