[PATCH v2 0/2] block/scsi: fix zones_cond out-of-bounds write on zone report

[PATCH v2 0/2] block/scsi: fix zones_cond out-of-bounds write on zone report

[ZHOU Jiaxiang]

blk_revalidate_disk_zones() sizes the zones_cond array from the disk
capacity and zone size, but the per-zone index used by
blk_revalidate_zone_cond() comes from the device-driven report_zones()
walk and is never checked against the array size. A device that reports
more zones than the array holds makes blk_zone_set_cond() write out of
bounds, one byte per extra zone.

A concrete way to reach it is a zone count that does not fit 32 bits:
both struct blk_revalidate_zone_args.nr_zones and struct
zoned_disk_info.nr_zones are unsigned int, so a disk advertising
2^32 + 1024 zones of one 512-byte logical block gets its count
truncated to 1024; the array is allocated for 1024 zones while the
report walk proceeds past index 1024.

This is structurally analogous to CVE-2025-40345 (a device-reported
value exceeding a capacity-derived table corrupts kernel heap) and,
like CVE-2024-47682, it is fed by target-supplied data in the sd
revalidation path. As in that report, note that sd also sits on network
transports (iSCSI/SRP/FCoE), so the malformed geometry can arrive from a
remote target, not only from a physically attached device.

Verified on commit 50d05c7c76c9 ("Merge tag 'landlock-7.3-rc3'
of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux"), which
is v7.3-rc2, using KASAN builds on x86_64 and arm64:

  BUG: KASAN: slab-out-of-bounds in blk_revalidate_zone_cb
  Write of size 1 ... 0 bytes to the right of allocated 1024-byte region
  sd_probe -> sd_revalidate_disk -> sd_zbc_revalidate_zones
    -> blk_revalidate_disk_zones -> sd_zbc_report_zones
    -> blk_revalidate_zone_cb

I have a working reproducer (dummy_hcd + raw-gadget ZBC device and a
minimal initramfs) as well as a full privilege-escalation demonstration
built on the primitive. As this report is the product of AI-assisted
analysis I am treating it as public per
Documentation/process/security-bugs.rst; both are available privately on
request.

Patch 1/2 fixes the write site and the block-layer truncation, which
covers every blk_revalidate_disk_zones() caller (sd, nvme, virtio-blk,
dm, null_blk, ublk, zloop). Patch 2/2 makes the SCSI path reject such
devices cleanly at scan time, before the truncated count reaches the
block layer.

Before the series the reproducer triggers the KASAN report above and the
escalation demonstration reaches a root shell from uid 1000. After the
series the device is rejected ("Too many zones"), there is no KASAN
report, and the demonstration no longer progresses. Each layer was also
verified independently (block-layer guard alone, and the write-site
check alone).

Changes in v2:
- patch 2/2: keep the single nr_zones variable, now u64, instead of
  adding a separate nr_zones64 temporary, as suggested by Damien.
  No functional change.
- patch 1/2: unchanged; carried Damien's Reviewed-by.

ZHOU Jiaxiang (2):
  block: fix zones_cond out-of-bounds write on zone report
  scsi: sd_zbc: reject disks with too many zones

 block/blk-zoned.c     | 15 +++++++++++++--
 drivers/scsi/sd_zbc.c |  8 +++++++-
 2 files changed, 20 insertions(+), 3 deletions(-)

--
2.50.1 (Apple Git-155)

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[PATCH v2 1/2] block: fix zones_cond out-of-bounds write on zone report

[ZHOU Jiaxiang]

blk_revalidate_disk_zones() sizes the zones_cond array from the disk
capacity and zone size, but the index used by blk_revalidate_zone_cond()
comes from the device-driven report_zones() walk and is never checked
against the array size. A device reporting more zones than fit the
array makes blk_zone_set_cond() write out of bounds.

One way to reach this is a zone count exceeding 32 bits: both
blk_revalidate_zone_args.nr_zones and struct zoned_disk_info.nr_zones
are unsigned int, so a disk advertising more than UINT_MAX zones (e.g.
2^32 + 1024 zones of one 512-byte logical block) gets its zone count
truncated to a small value, undersizing the array while the report
walk keeps counting upward.

Check the index against the array size before storing the zone
condition, and refuse to revalidate when the zone count does not fit
32 bits.

Fixes: 6e945ffb6555 ("block: use zone condition to determine conventional zones")
Signed-off-by: ZHOU Jiaxiang <26066541r@connect.polyu.hk>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
---
 block/blk-zoned.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index a5afb842b..475aa16bc 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -2018,12 +2018,17 @@ static int disk_revalidate_zone_resources(struct gendisk *disk,
                                struct blk_revalidate_zone_args *args)
 {
        struct queue_limits *lim = &disk->queue->limits;
+       unsigned long long nr_zones;
        unsigned int pool_size;
        int ret = 0;

        args->disk = disk;
-       args->nr_zones =
-               DIV_ROUND_UP_ULL(get_capacity(disk), lim->chunk_sectors);
+       nr_zones = DIV_ROUND_UP_ULL(get_capacity(disk), lim->chunk_sectors);
+       if (nr_zones > UINT_MAX) {
+               pr_warn("%s: Too many zones (%llu)\n", disk->disk_name, nr_zones);
+               return -EINVAL;
+       }
+       args->nr_zones = nr_zones;

        /* Cached zone conditions: 1 byte per zone */
        args->zones_cond = kzalloc(args->nr_zones, GFP_NOIO);
@@ -2131,6 +2136,12 @@ static int blk_revalidate_zone_cond(struct blk_zone *zone, unsigned int idx,
 {
        enum blk_zone_cond cond = zone->cond;

+       if (idx >= args->nr_zones) {
+               pr_warn("%s: Zone report index %u exceeds zone count %u\n",
+                       args->disk->disk_name, idx, args->nr_zones);
+               return -EINVAL;
+       }
+
        /* Check that the zone condition is consistent with the zone type. */
        switch (cond) {
        case BLK_ZONE_COND_NOT_WP:
--
2.50.1 (Apple Git-155)

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[PATCH v2 2/2] scsi: sd_zbc: reject disks with too many zones

[ZHOU Jiaxiang]

sd_zbc_read_zones() computes the number of zones with 64-bit
arithmetic and stores the result in the unsigned int nr_zones field
of struct zoned_disk_info, silently truncating counts that exceed 32
bits. The truncated count is later used to size per-zone resources,
while the device may still report more zones than fit.

Reject such devices at scan time: more than 4 billion zones is not
realistic for any medium that exists today, and accepting the
truncated count produces inconsistent zone bookkeeping.

Signed-off-by: ZHOU Jiaxiang <26066541r@connect.polyu.hk>
---
 drivers/scsi/sd_zbc.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
index 56e455fb5..f4570bd94 100644
--- a/drivers/scsi/sd_zbc.c
+++ b/drivers/scsi/sd_zbc.c
@@ -589,7 +589,7 @@ int sd_zbc_revalidate_zones(struct scsi_disk *sdkp)
 int sd_zbc_read_zones(struct scsi_disk *sdkp, struct queue_limits *lim,
                u8 buf[SD_BUF_SIZE])
 {
-       unsigned int nr_zones;
+       u64 nr_zones;
        u32 zone_blocks = 0;
        int ret;

@@ -621,6 +621,12 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, struct queue_limits *lim,
                goto err;

        nr_zones = round_up(sdkp->capacity, zone_blocks) >> ilog2(zone_blocks);
+       if (nr_zones > UINT_MAX) {
+               sd_printk(KERN_ERR, sdkp, "Too many zones (%llu)\n",
+                         nr_zones);
+               ret = -EINVAL;
+               goto err;
+       }
        sdkp->early_zone_info.nr_zones = nr_zones;
        sdkp->early_zone_info.zone_blocks = zone_blocks;

--
2.50.1 (Apple Git-155)

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The University specifically denies any responsibility for the accuracy or quality of information obtained through University E-mail Facilities. Any views and opinions expressed are only those of the author(s) and do not necessarily represent those of the University and the University accepts no liability whatsoever for any losses or damages incurred or caused to any party as a result of the use of such information.

Re: [PATCH v2 2/2] scsi: sd_zbc: reject disks with too many zones

[Damien Le Moal]

On 9/11/26 23:46, ZHOU Jiaxiang wrote:
> sd_zbc_read_zones() computes the number of zones with 64-bit
> arithmetic and stores the result in the unsigned int nr_zones field
> of struct zoned_disk_info, silently truncating counts that exceed 32
> bits. The truncated count is later used to size per-zone resources,
> while the device may still report more zones than fit.
> 
> Reject such devices at scan time: more than 4 billion zones is not
> realistic for any medium that exists today, and accepting the
> truncated count produces inconsistent zone bookkeeping.
> 
> Signed-off-by: ZHOU Jiaxiang <26066541r@connect.polyu.hk>

This needs a Fixes tag.
With that added, please feel free to add:

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 0/2] block/scsi: fix zones_cond out-of-bounds write on zone report

[Johannes Thumshirn]

For the series,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>