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.
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Daniel Borkmann <dborkman@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
---
Changes since v1:
- For sa >=32, load destination register with zero instead of treating
the immediate as 31
---
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,
--
2.0.0
