In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
null_blk: reject per-device queue resize for shared tag set<\/p>\n
When shared_tags is enabled, null_setup_tagset() makes the device use the
\nglobal tag_set, whose driver_data stays NULL. null_map_queues() therefore
\nfalls back to the module-wide g_submit_queues\/g_poll_queues instead of any
\nper-device value.<\/p>\n
Resizing submit_queues or poll_queues via configfs on such a device calls
\nblk_mq_update_nr_hw_queues() on the shared set, shrinking
\nset->nr_hw_queues. __blk_mq_realloc_hw_ctxs() only grows the
\nq->queue_hw_ctx[] allocation, so on shrink it merely exits and NULLs the
\nnow-excess hctx slots. null_map_queues(), however, keeps mapping CPUs with
\nthe unchanged g_submit_queues\/g_poll_queues, so mq_map[] ends up pointing
\nat those NULLed hctx slots. blk_mq_map_swqueue() then dereferences the NULL
\nhctx (hctx->cpumask), crashing the kernel:<\/p>\n
[ 460.218374] KASAN: null-ptr-deref in range [0x0000000000000098-0x000000000000009f]
\n[ 460.219003] CPU: 24 UID: 0 PID: 1492 Comm: sh Not tainted 7.2.0-rc2+ #67 PREEMPT(full)
\n[ 460.219792] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04\/01\/2014
\n[ 460.220452] RIP: 0010:blk_mq_map_swqueue+0x4db\/0x1430
\n……
\n[ 460.228977] Call Trace:
\n[ 460.229175]
\n[ 460.229354] blk_mq_update_nr_hw_queues+0xd49\/0x11c0
\n[ 460.229779] ? __pfx_blk_mq_update_nr_hw_queues+0x10\/0x10
\n[ 460.230200] nullb_update_nr_hw_queues+0x1a9\/0x370 [null_blk]
\n[ 460.230694] nullb_device_submit_queues_store+0xd9\/0x170 [null_blk]
\n[ 460.231190] ? __pfx_nullb_device_submit_queues_store+0x10\/0x10 [null_blk]
\n[ 460.231776] ? configfs_write_iter+0x35c\/0x4e0
\n[ 460.232122] configfs_write_iter+0x286\/0x4e0
\n[ 460.232460] vfs_write+0x52d\/0xd00
\n[ 460.232779] ? __x64_sys_openat+0x108\/0x1d0
\n[ 460.233106] ? __pfx_vfs_write+0x10\/0x10
\n[ 460.233413] ? fdget_pos+0x1cf\/0x4c0
\n[ 460.233745] ? fput_close+0x133\/0x190
\n[ 460.234038] ? __pfx_expand_files+0x10\/0x10
\n[ 460.234368] ksys_write+0xfc\/0x1d0<\/p>\n
Reproducer:
\nmodprobe null_blk shared_tags=1 submit_queues=64 poll_queues=1
\nmkdir \/sys\/kernel\/config\/nullb\/dev
\necho 1 > \/sys\/kernel\/config\/nullb\/dev\/power
\necho 1 > \/sys\/kernel\/config\/nullb\/dev\/submit_queues<\/p>\n
A per-device resize of a shared tag set is meaningless anyway, so reject it
\nwith -EINVAL in nullb_update_nr_hw_queues() when the device is bound to the
\nglobal tag_set.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
null_blk: reject per-device queue resize for shared tag set<\/p>\n
When shared_tags is enabled, null_setup_tagset() makes the device use <\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-25595","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/25595","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=25595"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=25595"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=25595"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}