LoongArch: BPF: Fix jump offset calculation in tailcall

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: LoongArch: BPF: Fix jump offset calculation in tailcall The extra pass of bpf_int_jit_compile() skips JIT context initialization which essentially skips offset calculation leaving out_offset = -1, so the jmp_offset in emit_bpf_tail_call is calculated by "#define jmp_offset (out_offset - (cur_offset))" is a negative number, which is wrong. The final generated assembly are as follow. 54: bgeu $a2, $t1, -8 # 0x0000004c 58: addi.d $a6, $s5, -1 5c: bltz $a6, -16 # 0x0000004c 60: alsl.d $t2, $a2, $a1, 0x3 64: ld.d $t2, $t2, 264 68: beq $t2, $zero, -28 # 0x0000004c Before apply this patch, the follow test case will reveal soft lock issues. cd tools/testing/selftests/bpf/ ./test_progs --allow=tailcalls/tailcall_bpf2bpf_1 dmesg: watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [test_progs:25056]

References

• https://git.kernel.org/stable/c/1a782fa32e644aa9fbae6c8488f3e61221ac96e1
• https://git.kernel.org/stable/c/17c010fe45def335fe03a0718935416b04c7f349
• https://git.kernel.org/stable/c/f83d469e16bb1f75991ca67c56786fb2aaa42bea
• https://git.kernel.org/stable/c/f2b5e50cc04d7a049b385bc1c93b9cbf5f10c94f
• https://git.kernel.org/stable/c/9262e3e04621558e875eb5afb5e726b648cd5949
• https://git.kernel.org/stable/c/cd39d9e6b7e4c58fa77783e7aedf7ada51d02ea3