Bug 2338817 (CVE-2025-21653) - CVE-2025-21653 kernel: net_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute
Summary: CVE-2025-21653 kernel: net_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute
Keywords:
Status: NEW
Alias: CVE-2025-21653
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2025-01-19 11:01 UTC by OSIDB Bzimport
Modified: 2025-01-21 15:15 UTC (History)
4 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


Attachments (Terms of Use)

Description OSIDB Bzimport 2025-01-19 11:01:30 UTC
In the Linux kernel, the following vulnerability has been resolved:

net_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute

syzbot found that TCA_FLOW_RSHIFT attribute was not validated.
Right shitfing a 32bit integer is undefined for large shift values.

UBSAN: shift-out-of-bounds in net/sched/cls_flow.c:329:23
shift exponent 9445 is too large for 32-bit type 'u32' (aka 'unsigned int')
CPU: 1 UID: 0 PID: 54 Comm: kworker/u8:3 Not tainted 6.13.0-rc3-syzkaller-00180-g4f619d518db9 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
 <TASK>
  __dump_stack lib/dump_stack.c:94 [inline]
  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
  ubsan_epilogue lib/ubsan.c:231 [inline]
  __ubsan_handle_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468
  flow_classify+0x24d5/0x25b0 net/sched/cls_flow.c:329
  tc_classify include/net/tc_wrapper.h:197 [inline]
  __tcf_classify net/sched/cls_api.c:1771 [inline]
  tcf_classify+0x420/0x1160 net/sched/cls_api.c:1867
  sfb_classify net/sched/sch_sfb.c:260 [inline]
  sfb_enqueue+0x3ad/0x18b0 net/sched/sch_sfb.c:318
  dev_qdisc_enqueue+0x4b/0x290 net/core/dev.c:3793
  __dev_xmit_skb net/core/dev.c:3889 [inline]
  __dev_queue_xmit+0xf0e/0x3f50 net/core/dev.c:4400
  dev_queue_xmit include/linux/netdevice.h:3168 [inline]
  neigh_hh_output include/net/neighbour.h:523 [inline]
  neigh_output include/net/neighbour.h:537 [inline]
  ip_finish_output2+0xd41/0x1390 net/ipv4/ip_output.c:236
  iptunnel_xmit+0x55d/0x9b0 net/ipv4/ip_tunnel_core.c:82
  udp_tunnel_xmit_skb+0x262/0x3b0 net/ipv4/udp_tunnel_core.c:173
  geneve_xmit_skb drivers/net/geneve.c:916 [inline]
  geneve_xmit+0x21dc/0x2d00 drivers/net/geneve.c:1039
  __netdev_start_xmit include/linux/netdevice.h:5002 [inline]
  netdev_start_xmit include/linux/netdevice.h:5011 [inline]
  xmit_one net/core/dev.c:3590 [inline]
  dev_hard_start_xmit+0x27a/0x7d0 net/core/dev.c:3606
  __dev_queue_xmit+0x1b73/0x3f50 net/core/dev.c:4434

Comment 1 Avinash Hanwate 2025-01-20 07:32:26 UTC
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025011947-CVE-2025-21653-b6c0@gregkh/T


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