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MIPS: BPF: Prevent kernel fall over for >=32bit shifts

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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>
This commit is contained in:
Markos Chandras 2014-06-25 09:37:21 +01:00 committed by Ralf Baechle
parent e5bb48b055
commit 95782bf434
1 changed files with 12 additions and 4 deletions
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16
arch/mips/net/bpf_jit.c
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@ -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,