Re: [PATCH v4] block: bio-integrity: Fix null-ptr-deref in bio_integrity_map_user()

[Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>]

On Apr 27, 2026 / 00:09, Sungwoo Kim wrote:
> 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.
> 
> Reproducer in blktest: https://github.com/linux-blktests/blktests/pull/244

The blktests Pull Request modifies the test case nvme/064 to write with 80KiB
size metadata. With this change, I confirmed that the Oops below was recreated
on my test system using the kernel v7.1-rc1.

> 
> 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>
> ---
> V3: https://lore.kernel.org/linux-block/20260420020327.1667156-3-iam@sung-woo.kim/
> 
> V3->V4
> - Addressed a sashiko's comments [1], if it makes sense.
> - V3 wrongly assumed that iov_iter_extract_pages() always pins user
>   memory.
> - V3 insufficiently handled the return value range.
> 
> [1] https://sashiko.dev/#/patchset/20260420020327.1667156-3-iam%40sung-woo.kim

I applied this v4 patch to v7.1-rc1 kernel. With this, I confirmed that the
Oops goes away. Looks good from testing point of view.

Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>