Subject: CVE-2024-35979: raid1: fix use-after-free for original bio in raid1_write_request()

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2024-35979 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.6 with commit 992db13a4aee and fixed in 6.6.28 with commit 3f28d49a328f
	Issue introduced in 6.6 with commit 992db13a4aee and fixed in 6.8.7 with commit f423f41b7679
	Issue introduced in 6.6 with commit 992db13a4aee and fixed in 6.9 with commit fcf3f7e2fc8a

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-35979
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/md/raid1.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/3f28d49a328fe20926995d5fbdc92da665596268
	https://git.kernel.org/stable/c/f423f41b7679c09abb26d2bd54be5cbef23c9446
	https://git.kernel.org/stable/c/fcf3f7e2fc8a53a6140beee46ec782a4c88e4744