cbcvebase.
CVE-2021-47584
published 2024-06-19

CVE-2021-47584: In the Linux kernel, the following vulnerability has been resolved: iocost: Fix divide-by-zero on donation from low hweight cgroup The donation calculation…

PriorityP420medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
EPSS
0.25%
16.4th percentile
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 0b 48 c7 c7 30 da ab b5 e8 71 3f fe ff 4c 89 e8 4d 85 ed 74 0 4 ... Call Trace: 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.

Affected

11 ranges
VendorProductVersion rangeFixed in
debianlinux< linux 5.15.15-1 (bookworm)linux 5.15.15-1 (bookworm)
linuxlinux——
linuxlinux>= f1de2439ec43b74764f2a26e3a310b24407e3bde < a7c80674538f15f85d68138240aae440b8039519a7c80674538f15f85d68138240aae440b8039519
linuxlinux>= f1de2439ec43b74764f2a26e3a310b24407e3bde < 3a1a4eb574178c21241a6200f4785572e661c4723a1a4eb574178c21241a6200f4785572e661c472
linuxlinux>= f1de2439ec43b74764f2a26e3a310b24407e3bde < edaa26334c117a584add6053f48d63a988d25a6eedaa26334c117a584add6053f48d63a988d25a6e
linuxlinux_kernel>= 0 < 5.10.92-15.10.92-1
linuxlinux_kernel>= 0 < 5.15.15-15.15.15-1
linuxlinux_kernel>= 0 < 5.15.15-15.15.15-1
linuxlinux_kernel>= 0 < 5.15.15-15.15.15-1
linuxlinux_kernel>= 5.10 < 5.10.885.10.88
linuxlinux_kernel>= 5.11 < 5.15.115.15.11

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
osv5.5MEDIUM
vendor_debian5.5MEDIUM
vendor_redhat5.5MEDIUM
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