CVE-2024-35979

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

raid1: fix use-after-free for original bio in raid1_write_request()

r1_bio->bios[] is used to record new bios that will be issued to

underlying disks, however, in raid1_write_request(), r1_bio->bios[]

will set to the original bio temporarily. Meanwhile, if blocked rdev

is set, free_r1bio() will be called causing that all r1_bio->bios[]

to be freed:

raid1_write_request()

r1_bio = alloc_r1bio(mddev, bio); -> r1_bio->bios[] is NULL

for (i = 0; i < disks; i++) -> for each rdev in conf

// first rdev is normal

r1_bio->bios[0] = bio; -> set to original bio

// second rdev is blocked

if (test_bit(Blocked, &rdev->flags))

break

if (blocked_rdev)

free_r1bio()

put_all_bios()

bio_put(r1_bio->bios[0]) -> original bio is freed

Test scripts:

mdadm -CR /dev/md0 -l1 -n4 /dev/sd[abcd] --assume-clean

fio -filename=/dev/md0 -ioengine=libaio -rw=write -bs=4k -numjobs=1 \

-iodepth=128 -name=test -direct=1

echo blocked > /sys/block/md0/md/rd2/state

Test result:

BUG bio-264 (Not tainted): Object already free

-----------------------------------------------------------------------------

Allocated in mempool_alloc_slab+0x24/0x50 age=1 cpu=1 pid=869

kmem_cache_alloc+0x324/0x480

mempool_alloc_slab+0x24/0x50

mempool_alloc+0x6e/0x220

bio_alloc_bioset+0x1af/0x4d0

blkdev_direct_IO+0x164/0x8a0

blkdev_write_iter+0x309/0x440

aio_write+0x139/0x2f0

io_submit_one+0x5ca/0xb70

__do_sys_io_submit+0x86/0x270

__x64_sys_io_submit+0x22/0x30

do_syscall_64+0xb1/0x210

entry_SYSCALL_64_after_hwframe+0x6c/0x74

Freed in mempool_free_slab+0x1f/0x30 age=1 cpu=1 pid=869

kmem_cache_free+0x28c/0x550

mempool_free_slab+0x1f/0x30

mempool_free+0x40/0x100

bio_free+0x59/0x80

bio_put+0xf0/0x220

free_r1bio+0x74/0xb0

raid1_make_request+0xadf/0x1150

md_handle_request+0xc7/0x3b0

md_submit_bio+0x76/0x130

__submit_bio+0xd8/0x1d0

submit_bio_noacct_nocheck+0x1eb/0x5c0

submit_bio_noacct+0x169/0xd40

submit_bio+0xee/0x1d0

blkdev_direct_IO+0x322/0x8a0

blkdev_write_iter+0x309/0x440

aio_write+0x139/0x2f0

Since that bios for underlying disks are not allocated yet, fix this

problem by using mempool_free() directly to free the r1_bio.