From: Hengqi Chen <hengqi.chen@gmail.com> stable inclusion from stable-v6.6.87 commit b3ffad2f02db4aace6799fe0049508b8925eae45 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IC2CC7 CVE: CVE-2025-37893 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 7e2586991e36663c9bc48c828b83eab180ad30a9 upstream. Vincent reported that running BPF progs with tailcalls on LoongArch causes kernel hard lockup. Debugging the issues shows that the JITed image missing a jirl instruction at the end of the epilogue. There are two passes in JIT compiling, the first pass set the flags and the second pass generates JIT code based on those flags. With BPF progs mixing bpf2bpf and tailcalls, build_prologue() generates N insns in the first pass and then generates N+1 insns in the second pass. This makes epilogue_offset off by one and we will jump to some unexpected insn and cause lockup. Fix this by inserting a nop insn. Cc: stable@vger.kernel.org Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support") Fixes: bb035ef0cc91 ("LoongArch: BPF: Support mixing bpf2bpf and tailcalls") Reported-by: Vincent Li <vincent.mc.li@gmail.com> Tested-by: Vincent Li <vincent.mc.li@gmail.com> Closes: https://lore.kernel.org/loongarch/CAK3+h2w6WESdBN3UCr3WKHByD7D6Q_Ve1EDAjotVr... Closes: https://lore.kernel.org/bpf/CAK3+h2woEjG_N=-XzqEGaAeCmgu2eTCUc7p6bP4u8Q+DFHm... Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Huang Xiaojia <huangxiaojia2@huawei.com> --- arch/loongarch/net/bpf_jit.c | 2 ++ arch/loongarch/net/bpf_jit.h | 5 +++++ 2 files changed, 7 insertions(+) diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c index 525fc03d7056..8312887eccaa 100644 --- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -142,6 +142,8 @@ static void build_prologue(struct jit_ctx *ctx) */ if (seen_tail_call(ctx) && seen_call(ctx)) move_reg(ctx, TCC_SAVED, REG_TCC); + else + emit_insn(ctx, nop); ctx->stack_size = stack_adjust; } diff --git a/arch/loongarch/net/bpf_jit.h b/arch/loongarch/net/bpf_jit.h index 68586338ecf8..f9c569f53949 100644 --- a/arch/loongarch/net/bpf_jit.h +++ b/arch/loongarch/net/bpf_jit.h @@ -27,6 +27,11 @@ struct jit_data { struct jit_ctx ctx; }; +static inline void emit_nop(union loongarch_instruction *insn) +{ + insn->word = INSN_NOP; +} + #define emit_insn(ctx, func, ...) \ do { \ if (ctx->image != NULL) { \ -- 2.34.1