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 <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>
diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index 1bcd599..9476e7f 100644
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -151,6 +151,8 @@
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 @@
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 @@
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,