CVE-2025-21653: net_sched: cls_flow: validate TCA_FLOW_RSHIFT attribute
Description
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:
__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/...
Classification
CVE ID: CVE-2025-21653
Affected Products
Vendor: Linux
Product: Linux
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.04% (probability of being exploited)
EPSS Percentile: 12.58% (scored less or equal to compared to others)
EPSS Date: 2025-02-17 (when was this score calculated)
References
https://git.kernel.org/stable/c/2011749ca96460386844dfc7e0fde53ebee96f3chttps://git.kernel.org/stable/c/e54beb9aed2a90dddf4c5d68fcfc9a01f3e40a61
https://git.kernel.org/stable/c/6fde663f7321418996645ee602a473457640542f
https://git.kernel.org/stable/c/a039e54397c6a75b713b9ce7894a62e06956aa92