CVE-2023-53791: 
Linux Kernel vulnerability analysis and mitigation

In the Linux kernel, the following vulnerability has been resolved:

md: fix warning for holder mismatch from export_rdev()

Commit a1d767191096 ("md: use mddev->external to select holder in export_rdev()") fix the problem that 'claim_rdev' is used for blkdev_get_by_dev() while 'rdev' is used for blkdev_put().

However, if mddev->external is changed from 0 to 1, then 'rdev' is used for blkdev_get_by_dev() while 'claim_rdev' is used for blkdev_put(). And this problem can be reporduced reliably by following:

New file: mdadm/tests/23rdev-lifetime

devname=${dev0##*/} devt=cat /sys/block/$devname/dev pid="" runtime=2

clean_up_test() { pill -9 $pid echo clear > /sys/block/md0/md/array_state }

trap 'clean_up_test' EXIT

add_by_sysfs() { while true; do echo $devt > /sys/block/md0/md/new_dev done }

remove_by_sysfs(){ while true; do echo remove > /sys/block/md0/md/dev-${devname}/state done }

echo md0 > /sys/module/md_mod/parameters/new_array || die "create md0 failed"

add_by_sysfs & pid="$pid $!"

remove_by_sysfs & pid="$pid $!"

sleep $runtime exit 0

Test cmd:

./test --save-logs --logdir=/tmp/ --keep-going --dev=loop --tests=23rdev-lifetime

Test result:

------------[ cut here ]------------ WARNING: CPU: 0 PID: 960 at block/bdev.c:618 blkdev_put+0x27c/0x330 Modules linked in: multipath md_mod loop CPU: 0 PID: 960 Comm: test Not tainted 6.5.0-rc2-00121-g01e55c376936-dirty #50 RIP: 0010:blkdev_put+0x27c/0x330 Call Trace: export_rdev.isra.23+0x50/0xa0 [md_mod] mddev_unlock+0x19d/0x300 [md_mod] rdev_attr_store+0xec/0x190 [md_mod] sysfs_kf_write+0x52/0x70 kernfs_fop_write_iter+0x19a/0x2a0 vfs_write+0x3b5/0x770 ksys_write+0x74/0x150 __x64_sys_write+0x22/0x30 do_syscall_64+0x40/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fix the problem by recording if 'rdev' is used as holder.