block: bio-integrity: Fix null-ptr-deref in bio_integrity_map_user()

pin_user_pages_fast() can partially succeed and return the number of
pages that were actually pinned. However, the bio_integrity_map_user()
does not handle this partial pinning. This leads to a general protection
fault since bvec_from_pages() dereferences an unpinned page address,
which is 0.

To fix this, add a check to verify that all requested memory is pinned.
If partial pinning occurs, unpin the memory and return -EFAULT.

Kernel Oops:

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 UID: 0 PID: 1061 Comm: nvme-passthroug Not tainted 7.0.0-11783-g90957f9314e8-dirty #16 PREEMPT(lazy)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
RIP: 0010:bio_integrity_map_user.cold+0x1b0/0x9d6

Fixes: 492c5d455969 ("block: bio-integrity: directly map user buffers")
Acked-by: Chao Shi <cshi008@fiu.edu>
Acked-by: Weidong Zhu <weizhu@fiu.edu>
Acked-by: Dave Tian <daveti@purdue.edu>
Signed-off-by: Sungwoo Kim <iam@sung-woo.kim>
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Link: https://github.com/linux-blktests/blktests/pull/244
Link: https://patch.msgid.link/20260512050929.541397-2-iam@sung-woo.kim
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index 78e678d4104b69f6602c6253cf42d1c0e52f2bf0..e796de1a749e335b01e24a7c074fa724eaada4fc 100644 (file)
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -402,6 +402,24 @@ int bio_integrity_map_user(struct bio *bio, struct iov_iter *iter)
        if (unlikely(ret < 0))
                goto free_bvec;
 
+       /*
+        * Handle partial pinning. This can happen when pin_user_pages_fast()
+        * returns fewer pages than requested.
+        */
+       if (user_backed_iter(iter) && unlikely(ret != bytes)) {
+               if (ret > 0) {
+                       int npinned = DIV_ROUND_UP(offset + ret, PAGE_SIZE);
+                       int i;
+
+                       for (i = 0; i < npinned; i++)
+                               unpin_user_page(pages[i]);
+               }
+               if (pages != stack_pages)
+                       kvfree(pages);
+               ret = -EFAULT;
+               goto free_bvec;
+       }
+
        nr_bvecs = bvec_from_pages(bvec, pages, nr_vecs, bytes, offset,
                                   &is_p2p);
        if (pages != stack_pages)