SUSE: CVE-2021-47584: SUSE Linux Security Advisory
Description
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.
Solution(s)
- suse-upgrade-cluster-md-kmp-azure
- suse-upgrade-cluster-md-kmp-rt
- suse-upgrade-dlm-kmp-azure
- suse-upgrade-dlm-kmp-rt
- suse-upgrade-gfs2-kmp-azure
- suse-upgrade-gfs2-kmp-rt
- suse-upgrade-kernel-azure
- suse-upgrade-kernel-azure-devel
- suse-upgrade-kernel-azure-extra
- suse-upgrade-kernel-azure-livepatch-devel
- suse-upgrade-kernel-azure-optional
- suse-upgrade-kernel-azure-vdso
- suse-upgrade-kernel-devel-azure
- suse-upgrade-kernel-devel-rt
- suse-upgrade-kernel-rt
- suse-upgrade-kernel-rt-devel
- suse-upgrade-kernel-rt-extra
- suse-upgrade-kernel-rt-livepatch
- suse-upgrade-kernel-rt-livepatch-devel
- suse-upgrade-kernel-rt-optional
- suse-upgrade-kernel-rt-vdso
- suse-upgrade-kernel-rt_debug
- suse-upgrade-kernel-rt_debug-devel
- suse-upgrade-kernel-rt_debug-livepatch-devel
- suse-upgrade-kernel-rt_debug-vdso
- suse-upgrade-kernel-source-azure
- suse-upgrade-kernel-source-rt
- suse-upgrade-kernel-syms-azure
- suse-upgrade-kernel-syms-rt
- suse-upgrade-kselftests-kmp-azure
- suse-upgrade-kselftests-kmp-rt
- suse-upgrade-ocfs2-kmp-azure
- suse-upgrade-ocfs2-kmp-rt
- suse-upgrade-reiserfs-kmp-azure
- suse-upgrade-reiserfs-kmp-rt
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