CVE-2025-40079 is a low severity vulnerability with a CVSS score of 0.0. No known exploits currently, and patches are available.
Very low probability of exploitation
EPSS predicts the probability of exploitation in the next 30 days based on real-world threat data, complementing CVSS severity scores with actual risk assessment.
In the Linux kernel, the following vulnerability has been resolved:
riscv, bpf: Sign extend struct ops return values properly
The ns_bpf_qdisc selftest triggers a kernel panic:
Unable to handle kernel paging request at virtual address ffffffffa38dbf58
Current test_progs pgtable: 4K pagesize, 57-bit VAs, pgdp=0x00000001109cc000
[ffffffffa38dbf58] pgd=000000011fffd801, p4d=000000011fffd401, pud=000000011fffd001, pmd=0000000000000000
Oops [#1]
Modules linked in: bpf_testmod(OE) xt_conntrack nls_iso8859_1 [...] [last unloaded: bpf_testmod(OE)]
CPU: 1 UID: 0 PID: 23584 Comm: test_progs Tainted: G W OE 6.17.0-rc1-g2465bb83e0b4 #1 NONE
Tainted: [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: Unknown Unknown Product/Unknown Product, BIOS 2024.01+dfsg-1ubuntu5.1 01/01/2024
epc : __qdisc_run+0x82/0x6f0
ra : __qdisc_run+0x6e/0x6f0
epc : ffffffff80bd5c7a ra : ffffffff80bd5c66 sp : ff2000000eecb550
gp : ffffffff82472098 tp : ff60000096895940 t0 : ffffffff8001f180
t1 : ffffffff801e1664 t2 : 0000000000000000 s0 : ff2000000eecb5d0
s1 : ff60000093a6a600 a0 : ffffffffa38dbee8 a1 : 0000000000000001
a2 : ff2000000eecb510 a3 : 0000000000000001 a4 : 0000000000000000
a5 : 0000000000000010 a6 : 0000000000000000 a7 : 0000000000735049
s2 : ffffffffa38dbee8 s3 : 0000000000000040 s4 : ff6000008bcda000
s5 : 0000000000000008 s6 : ff60000093a6a680 s7 : ff60000093a6a6f0
s8 : ff60000093a6a6ac s9 : ff60000093140000 s10: 0000000000000000
s11: ff2000000eecb9d0 t3 : 0000000000000000 t4 : 0000000000ff0000
t5 : 0000000000000000 t6 : ff60000093a6a8b6
status: 0000000200000120 badaddr: ffffffffa38dbf58 cause: 000000000000000d
[<ffffffff80bd5c7a>] __qdisc_run+0x82/0x6f0
[<ffffffff80b6fe58>] __dev_queue_xmit+0x4c0/0x1128
[<ffffffff80b80ae0>] neigh_resolve_output+0xd0/0x170
[<ffffffff80d2daf6>] ip6_finish_output2+0x226/0x6c8
[<ffffffff80d31254>] ip6_finish_output+0x10c/0x2a0
[<ffffffff80d31446>] ip6_output+0x5e/0x178
[<ffffffff80d2e232>] ip6_xmit+0x29a/0x608
[<ffffffff80d6f4c6>] inet6_csk_xmit+0xe6/0x140
[<ffffffff80c985e4>] __tcp_transmit_skb+0x45c/0xaa8
[<ffffffff80c995fe>] tcp_connect+0x9ce/0xd10
[<ffffffff80d66524>] tcp_v6_connect+0x4ac/0x5e8
[<ffffffff80cc19b8>] __inet_stream_connect+0xd8/0x318
[<ffffffff80cc1c36>] inet_stream_connect+0x3e/0x68
[<ffffffff80b42b20>] __sys_connect_file+0x50/0x88
[<ffffffff80b42bee>] __sys_connect+0x96/0xc8
[<ffffffff80b42c40>] __riscv_sys_connect+0x20/0x30
[<ffffffff80e5bcae>] do_trap_ecall_u+0x256/0x378
[<ffffffff80e69af2>] handle_exception+0x14a/0x156
Code: 892a 0363 1205 489c 8bc1 c7e5 2d03 084a 2703 080a (2783) 0709
---[ end trace 0000000000000000 ]---
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The bpf_fifo_dequeue prog returns a skb which is a pointer. The pointer is treated as a 32bit value and sign extend to 64bit in epilogue. This behavior is right for most bpf prog types but wrong for struct ops which requires RISC-V ABI.
So let's sign extend struct ops return values according to the function model and RISC-V ABI(0).