[PATCH] powerpc/lib: Validate size for vector operations

[Naveen N Rao]

Some of the fp/vmx code in sstep.c assume a certain maximum size for the
instructions being emulated. The size of those operations however is
determined separately in analyse_instr().

Add a check to validate the assumption on the maximum size of the
operations, so as to prevent any unintended kernel stack corruption.

Signed-off-by: Naveen N Rao <nav...@kernel.org>
---
 arch/powerpc/lib/sstep.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index a13f05cfc7db..5766180f5380 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -586,6 +586,8 @@ static int do_fp_load(struct instruction_op *op, unsigned 
long ea,
        } u;
 
        nb = GETSIZE(op->type);
+       if (nb > sizeof(u))
+               return -EINVAL;
        if (!address_ok(regs, ea, nb))
                return -EFAULT;
        rn = op->reg;
@@ -636,6 +638,8 @@ static int do_fp_store(struct instruction_op *op, unsigned 
long ea,
        } u;
 
        nb = GETSIZE(op->type);
+       if (nb > sizeof(u))
+               return -EINVAL;
        if (!address_ok(regs, ea, nb))
                return -EFAULT;
        rn = op->reg;
@@ -680,6 +684,9 @@ static nokprobe_inline int do_vec_load(int rn, unsigned 
long ea,
                u8 b[sizeof(__vector128)];
        } u = {};
 
+       if (size > sizeof(u))
+               return -EINVAL;
+
        if (!address_ok(regs, ea & ~0xfUL, 16))
                return -EFAULT;
        /* align to multiple of size */
@@ -707,6 +714,9 @@ static nokprobe_inline int do_vec_store(int rn, unsigned 
long ea,
                u8 b[sizeof(__vector128)];
        } u;
 
+       if (size > sizeof(u))
+               return -EINVAL;
+
        if (!address_ok(regs, ea & ~0xfUL, 16))
                return -EFAULT;
        /* align to multiple of size */

base-commit: 275f51172646ac48f0c4e690c72183084fd996d1
prerequisite-patch-id: ebc3edfe2b9fce7bdf27098c8631740153249b06
-- 
2.42.0