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riscv, bpf: Sign extend struct ops return values properly

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[ Upstream commit fd2e08128944a7679e753f920e9eda72057e427c ]

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 ]---

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]).

  [0]: https://riscv.org/wp-content/uploads/2024/12/riscv-calling.pdf

Fixes: 25ad10658d ("riscv, bpf: Adapt bpf trampoline to optimized riscv ftrace framework")
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Pu Lehui <pulehui@huawei.com>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Link: https://lore.kernel.org/bpf/20250908012448.1695-1-hengqi.chen@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Hengqi Chen 2025-09-08 01:24:48 +00:00 committed by Greg Kroah-Hartman
parent f955ceecfc
commit 92751937f1
1 changed files with 41 additions and 1 deletions
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42
arch/riscv/net/bpf_jit_comp64.c
View File

@ -559,6 +559,39 @@ static void emit_atomic(u8 rd, u8 rs, s16 off, s32 imm, bool is64,
}
}
/*
* Sign-extend the register if necessary
*/
static int sign_extend(u8 rd, u8 rs, u8 sz, bool sign, struct rv_jit_context *ctx)
{
if (!sign && (sz == 1 || sz == 2)) {
if (rd != rs)
emit_mv(rd, rs, ctx);
return 0;
}
switch (sz) {
case 1:
emit_sextb(rd, rs, ctx);
break;
case 2:
emit_sexth(rd, rs, ctx);
break;
case 4:
emit_sextw(rd, rs, ctx);
break;
case 8:
if (rd != rs)
emit_mv(rd, rs, ctx);
break;
default:
pr_err("bpf-jit: invalid size %d for sign_extend\n", sz);
return -EINVAL;
}
return 0;
}
#define BPF_FIXUP_OFFSET_MASK GENMASK(26, 0)
#define BPF_FIXUP_REG_MASK GENMASK(31, 27)
#define REG_DONT_CLEAR_MARKER 0 /* RV_REG_ZERO unused in pt_regmap */
@ -1020,8 +1053,15 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
restore_args(min_t(int, nr_arg_slots, RV_MAX_REG_ARGS), args_off, ctx);
if (save_ret) {
emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx);
emit_ld(regmap[BPF_REG_0], -(retval_off - 8), RV_REG_FP, ctx);
if (is_struct_ops) {
ret = sign_extend(RV_REG_A0, regmap[BPF_REG_0], m->ret_size,
m->ret_flags & BTF_FMODEL_SIGNED_ARG, ctx);
if (ret)
goto out;
} else {
emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx);
}
}
emit_ld(RV_REG_S1, -sreg_off, RV_REG_FP, ctx);