6.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Hengqi Chen hengqi.chen@gmail.com
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 --- arch/loongarch/net/bpf_jit.c | 2 ++ arch/loongarch/net/bpf_jit.h | 5 +++++ 2 files changed, 7 insertions(+)
--- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -142,6 +142,8 @@ static void build_prologue(struct jit_ct */ 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; } --- 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) { \