CVE-2025-38723

In the Linux kernel, the following vulnerability has been resolved:

LoongArch: BPF: Fix jump offset calculation in tailcall

The extra pass of bpfintjitcompile() skips JIT context initialization which essentially skips offset calculation leaving outoffset = -1, so the jmpoffset in emitbpftailcall is calculated by

"#define jmpoffset (outoffset - (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/ ./testprogs --allow=tailcalls/tailcallbpf2bpf_1

dmesg: watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [test_progs:25056]