MIPS: BPF: Prevent kernel fall over for >=32bit shifts (95782bf4) · Commits · 戴 / test

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 <markos.chandras@imgtec.com> Cc: David S. Miller <davem@davemloft.net> Cc: Daniel Borkmann <dborkman@redhat.com> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: netdev@vger.kernel.org Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/7179/ Signed-off-by:

Ralf Baechle <ralf@linux-mips.org>

arch/mips/net/bpf_jit.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -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 { \
		@@ -309,7 +311,10 @@ 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));
		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);
		}

		@@ -323,7 +328,10 @@ 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));
		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);
		}

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