powerpc/lib: Validate size for vector operations

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 <naveen@kernel.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Build-tested-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231123071705.397625-1-naveen@kernel.org

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index a13f05cfc7db67052a8c81b96f9b47fcb771e06e..5766180f5380a6f2b8f90c4f31de3019991bf65f 100644 (file)
--- 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 */