From 95782bf434437b3292f5cb9ce21b53bdbc1beda1 Mon Sep 17 00:00:00 2001 From: Markos Chandras Date: Wed, 25 Jun 2014 09:37:21 +0100 Subject: [PATCH] MIPS: BPF: Prevent kernel fall over for >=32bit shifts Remove BUG_ON() if the shift immediate is >=32 to avoid kernel crashes due to malicious user input. If the shift immediate is >= 32, we simply load the destination register with 0 since only 32-bit instructions are used by JIT so this will do the correct thing even on MIPS64. Signed-off-by: Markos Chandras Cc: David S. Miller Cc: Daniel Borkmann Cc: Alexei Starovoitov Cc: netdev@vger.kernel.org Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/7179/ Signed-off-by: Ralf Baechle --- arch/mips/net/bpf_jit.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c index 1bcd599d9971..9476e7f061a1 100644 --- a/arch/mips/net/bpf_jit.c +++ b/arch/mips/net/bpf_jit.c @@ -151,6 +151,8 @@ static inline int optimize_div(u32 *k) return 0; } +static inline void emit_jit_reg_move(ptr dst, ptr src, struct jit_ctx *ctx); + /* Simply emit the instruction if the JIT memory space has been allocated */ #define emit_instr(ctx, func, ...) \ do { \ @@ -309,8 +311,11 @@ static inline void emit_sll(unsigned int dst, unsigned int src, unsigned int sa, struct jit_ctx *ctx) { /* sa is 5-bits long */ - BUG_ON(sa >= BIT(5)); - emit_instr(ctx, sll, dst, src, sa); + if (sa >= BIT(5)) + /* Shifting >= 32 results in zero */ + emit_jit_reg_move(dst, r_zero, ctx); + else + emit_instr(ctx, sll, dst, src, sa); } static inline void emit_srlv(unsigned int dst, unsigned int src, @@ -323,8 +328,11 @@ static inline void emit_srl(unsigned int dst, unsigned int src, unsigned int sa, struct jit_ctx *ctx) { /* sa is 5-bits long */ - BUG_ON(sa >= BIT(5)); - emit_instr(ctx, srl, dst, src, sa); + if (sa >= BIT(5)) + /* Shifting >= 32 results in zero */ + emit_jit_reg_move(dst, r_zero, ctx); + else + emit_instr(ctx, srl, dst, src, sa); } static inline void emit_slt(unsigned int dst, unsigned int src1, -- 2.39.5