Security update for the Linux Kernel (Live Patch 11 for SLE 15 SP6) SUSE Patch security@suse.de SUSE Security Team SUSE-SU-2025:02693-1 Final 1 1 2025-08-05T07:34:42Z current 2025-08-05T07:34:42Z 2025-08-05T07:34:42Z cve-database/bin/generate-cvrf.pl 2017-02-24T01:00:00Z Security update for the Linux Kernel (Live Patch 11 for SLE 15 SP6) This update for the Linux Kernel 6.4.0-150600_23_50 fixes several issues. The following security issues were fixed: - CVE-2025-37797: net_sched: hfsc: Fix a UAF vulnerability in class handling (bsc#1245793). - CVE-2025-37752: net_sched: sch_sfq: move the limit validation (bsc#1245776). - CVE-2025-21702: pfifo_tail_enqueue: Drop new packet when sch->limit == 0 (bsc#1245797). The CVRF data is provided by SUSE under the Creative Commons License 4.0 with Attribution (CC-BY-4.0). SUSE-2025-2693,SUSE-SLE-Module-Live-Patching-15-SP6-2025-2693 Copyright SUSE LLC under the Creative Commons License 4.0 with Attribution (CC-BY-4.0) https://www.suse.com/support/update/announcement/2025/suse-su-202502693-1/ Link for SUSE-SU-2025:02693-1 https://lists.suse.com/pipermail/sle-updates/2025-August/041086.html E-Mail link for SUSE-SU-2025:02693-1 https://www.suse.com/support/security/rating/ SUSE Security Ratings https://bugzilla.suse.com/1244337 SUSE Bug 1244337 https://bugzilla.suse.com/1245776 SUSE Bug 1245776 https://bugzilla.suse.com/1245793 SUSE Bug 1245793 https://bugzilla.suse.com/1245797 SUSE Bug 1245797 https://www.suse.com/security/cve/CVE-2025-21702/ SUSE CVE CVE-2025-21702 page https://www.suse.com/security/cve/CVE-2025-37752/ SUSE CVE CVE-2025-37752 page https://www.suse.com/security/cve/CVE-2025-37797/ SUSE CVE CVE-2025-37797 page SUSE Linux Enterprise Live Patching 15 SP6 kernel-livepatch-6_4_0-150600_23_50-default-2-150600.2.1 kernel-livepatch-6_4_0-150600_23_50-default-2-150600.2.1 as a component of SUSE Linux Enterprise Live Patching 15 SP6 In the Linux kernel, the following vulnerability has been resolved: pfifo_tail_enqueue: Drop new packet when sch->limit == 0 Expected behaviour: In case we reach scheduler's limit, pfifo_tail_enqueue() will drop a packet in scheduler's queue and decrease scheduler's qlen by one. Then, pfifo_tail_enqueue() enqueue new packet and increase scheduler's qlen by one. Finally, pfifo_tail_enqueue() return `NET_XMIT_CN` status code. Weird behaviour: In case we set `sch->limit == 0` and trigger pfifo_tail_enqueue() on a scheduler that has no packet, the 'drop a packet' step will do nothing. This means the scheduler's qlen still has value equal 0. Then, we continue to enqueue new packet and increase scheduler's qlen by one. In summary, we can leverage pfifo_tail_enqueue() to increase qlen by one and return `NET_XMIT_CN` status code. The problem is: Let's say we have two qdiscs: Qdisc_A and Qdisc_B. - Qdisc_A's type must have '->graft()' function to create parent/child relationship. Let's say Qdisc_A's type is `hfsc`. Enqueue packet to this qdisc will trigger `hfsc_enqueue`. - Qdisc_B's type is pfifo_head_drop. Enqueue packet to this qdisc will trigger `pfifo_tail_enqueue`. - Qdisc_B is configured to have `sch->limit == 0`. - Qdisc_A is configured to route the enqueued's packet to Qdisc_B. Enqueue packet through Qdisc_A will lead to: - hfsc_enqueue(Qdisc_A) -> pfifo_tail_enqueue(Qdisc_B) - Qdisc_B->q.qlen += 1 - pfifo_tail_enqueue() return `NET_XMIT_CN` - hfsc_enqueue() check for `NET_XMIT_SUCCESS` and see `NET_XMIT_CN` => hfsc_enqueue() don't increase qlen of Qdisc_A. The whole process lead to a situation where Qdisc_A->q.qlen == 0 and Qdisc_B->q.qlen == 1. Replace 'hfsc' with other type (for example: 'drr') still lead to the same problem. This violate the design where parent's qlen should equal to the sum of its childrens'qlen. Bug impact: This issue can be used for user->kernel privilege escalation when it is reachable. CVE-2025-21702 SUSE Linux Enterprise Live Patching 15 SP6:kernel-livepatch-6_4_0-150600_23_50-default-2-150600.2.1 important To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch". https://www.suse.com/support/update/announcement/2025/suse-su-202502693-1/ https://www.suse.com/security/cve/CVE-2025-21702.html CVE-2025-21702 https://bugzilla.suse.com/1237312 SUSE Bug 1237312 https://bugzilla.suse.com/1245797 SUSE Bug 1245797 In the Linux kernel, the following vulnerability has been resolved: net_sched: sch_sfq: move the limit validation It is not sufficient to directly validate the limit on the data that the user passes as it can be updated based on how the other parameters are changed. Move the check at the end of the configuration update process to also catch scenarios where the limit is indirectly updated, for example with the following configurations: tc qdisc add dev dummy0 handle 1: root sfq limit 2 flows 1 depth 1 tc qdisc add dev dummy0 handle 1: root sfq limit 2 flows 1 divisor 1 This fixes the following syzkaller reported crash: ------------[ cut here ]------------ UBSAN: array-index-out-of-bounds in net/sched/sch_sfq.c:203:6 index 65535 is out of range for type 'struct sfq_head[128]' CPU: 1 UID: 0 PID: 3037 Comm: syz.2.16 Not tainted 6.14.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x201/0x300 lib/dump_stack.c:120 ubsan_epilogue lib/ubsan.c:231 [inline] __ubsan_handle_out_of_bounds+0xf5/0x120 lib/ubsan.c:429 sfq_link net/sched/sch_sfq.c:203 [inline] sfq_dec+0x53c/0x610 net/sched/sch_sfq.c:231 sfq_dequeue+0x34e/0x8c0 net/sched/sch_sfq.c:493 sfq_reset+0x17/0x60 net/sched/sch_sfq.c:518 qdisc_reset+0x12e/0x600 net/sched/sch_generic.c:1035 tbf_reset+0x41/0x110 net/sched/sch_tbf.c:339 qdisc_reset+0x12e/0x600 net/sched/sch_generic.c:1035 dev_reset_queue+0x100/0x1b0 net/sched/sch_generic.c:1311 netdev_for_each_tx_queue include/linux/netdevice.h:2590 [inline] dev_deactivate_many+0x7e5/0xe70 net/sched/sch_generic.c:1375 CVE-2025-37752 SUSE Linux Enterprise Live Patching 15 SP6:kernel-livepatch-6_4_0-150600_23_50-default-2-150600.2.1 important To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch". https://www.suse.com/support/update/announcement/2025/suse-su-202502693-1/ https://www.suse.com/security/cve/CVE-2025-37752.html CVE-2025-37752 https://bugzilla.suse.com/1242504 SUSE Bug 1242504 https://bugzilla.suse.com/1245776 SUSE Bug 1245776 In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class handling This patch fixes a Use-After-Free vulnerability in the HFSC qdisc class handling. The issue occurs due to a time-of-check/time-of-use condition in hfsc_change_class() when working with certain child qdiscs like netem or codel. The vulnerability works as follows: 1. hfsc_change_class() checks if a class has packets (q.qlen != 0) 2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g., codel, netem) might drop packets and empty the queue 3. The code continues assuming the queue is still non-empty, adding the class to vttree 4. This breaks HFSC scheduler assumptions that only non-empty classes are in vttree 5. Later, when the class is destroyed, this can lead to a Use-After-Free The fix adds a second queue length check after qdisc_peek_len() to verify the queue wasn't emptied. CVE-2025-37797 SUSE Linux Enterprise Live Patching 15 SP6:kernel-livepatch-6_4_0-150600_23_50-default-2-150600.2.1 important To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch". https://www.suse.com/support/update/announcement/2025/suse-su-202502693-1/ https://www.suse.com/security/cve/CVE-2025-37797.html CVE-2025-37797 https://bugzilla.suse.com/1242417 SUSE Bug 1242417 https://bugzilla.suse.com/1245793 SUSE Bug 1245793