{"timestamp":"2024-06-20T19:43:49.047356Z","id":"CVE-2021-47584","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}

[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","programFiles":["block/blk-iocost.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"f1de2439ec43b74764f2a26e3a310b24407e3bde","lessThan":"a7c80674538f15f85d68138240aae440b8039519","versionType":"git","status":"affected"},{"version":"f1de2439ec43b74764f2a26e3a310b24407e3bde","lessThan":"3a1a4eb574178c21241a6200f4785572e661c472","versionType":"git","status":"affected"},{"version":"f1de2439ec43b74764f2a26e3a310b24407e3bde","lessThan":"edaa26334c117a584add6053f48d63a988d25a6e","versionType":"git","status":"affected"}]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","programFiles":["block/blk-iocost.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"5.10","status":"affected"},{"version":"0","lessThan":"5.10","versionType":"semver","status":"unaffected"},{"version":"5.10.88","lessThanOrEqual":"5.10.*","versionType":"semver","status":"unaffected"},{"version":"5.15.11","lessThanOrEqual":"5.15.*","versionType":"semver","status":"unaffected"},{"version":"5.16","lessThanOrEqual":"*","versionType":"original_commit_for_fix","status":"unaffected"}]}]

https://git.kernel.org/stable/c/3a1a4eb574178c21241a6200f4785572e661c472

https://git.kernel.org/stable/c/a7c80674538f15f85d68138240aae440b8039519

https://git.kernel.org/stable/c/edaa26334c117a584add6053f48d63a988d25a6e

NIST AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NIST CWE-369

OR
     *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.10 up to (excluding) 5.10.88
     *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.11 up to (excluding) 5.15.11

https://git.kernel.org/stable/c/3a1a4eb574178c21241a6200f4785572e661c472 No Types Assigned

https://git.kernel.org/stable/c/3a1a4eb574178c21241a6200f4785572e661c472 Patch

https://git.kernel.org/stable/c/a7c80674538f15f85d68138240aae440b8039519 No Types Assigned

https://git.kernel.org/stable/c/a7c80674538f15f85d68138240aae440b8039519 Patch

https://git.kernel.org/stable/c/edaa26334c117a584add6053f48d63a988d25a6e No Types Assigned

https://git.kernel.org/stable/c/edaa26334c117a584add6053f48d63a988d25a6e Patch

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

iocost: Fix divide-by-zero on donation from low hweight cgroup

The donation calculation logic assumes that the donor has non-zero
after-donation hweight, so the lowest active hweight a donating cgroup can
have is 2 so that it can donate 1 while keeping the other 1 for itself.
Earlier, we only donated from cgroups with sizable surpluses so this
condition was always true. However, with the precise donation algorithm
implemented, f1de2439ec43 ("blk-iocost: revamp donation amount
determination") made the donation amount calculation exact enabling even low
hweight cgroups to donate.

This means that in rare occasions, a cgroup with active hweight of 1 can
enter donation calculation triggering the following warning and then a
divide-by-zero oops.

 WARNING: CPU: 4 PID: 0 at block/blk-iocost.c:1928 transfer_surpluses.cold+0x0/0x53 [884/94867]
 ...
 RIP: 0010:transfer_surpluses.cold+0x0/0x53
 Code: 92 ff 48 c7 c7 28 d1 ab b5 65 48 8b 34 25 00 ae 01 00 48 81 c6 90 06 00 00 e8 8b 3f fe ff 48 c7 c0 ea ff ff ff e9 95 ff 92 ff <0f> 0b 48 c7 c7 30 da ab b5 e8 71 3f fe ff 4c 89 e8 4d 85 ed 74 0
4
 ...
 Call Trace:
  <IRQ>
  ioc_timer_fn+0x1043/0x1390
  call_timer_fn+0xa1/0x2c0
  __run_timers.part.0+0x1ec/0x2e0
  run_timer_softirq+0x35/0x70
 ...
 iocg: invalid donation weights in /a/b: active=1 donating=1 after=0

Fix it by excluding cgroups w/ active hweight < 2 from donating. Excluding
these extreme low hweight donations shouldn't affect work conservation in
any meaningful way.

kernel.org https://git.kernel.org/stable/c/3a1a4eb574178c21241a6200f4785572e661c472 [No types assigned]

kernel.org https://git.kernel.org/stable/c/a7c80674538f15f85d68138240aae440b8039519 [No types assigned]

kernel.org https://git.kernel.org/stable/c/edaa26334c117a584add6053f48d63a988d25a6e [No types assigned]