Re: [v4] Fix to avoid IS_ERR_VALUE and IS_ERR abuses on 64bit systems.

On Wednesday 03 August 2016 01:27 AM, Scott Wood wrote:

On 08/02/2016 10:34 AM, arvind Yadav wrote:

quoted

On Tuesday 02 August 2016 01:15 PM, Arnd Bergmann wrote:

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On Monday, August 1, 2016 4:55:43 PM CEST Scott Wood wrote:

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On 08/01/2016 02:02 AM, Arnd Bergmann wrote:

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diff --git a/include/linux/err.h b/include/linux/err.h
index 1e35588..c2a2789 100644
--- a/include/linux/err.h
+++ b/include/linux/err.h

@@ -18,7 +18,17 @@
  
  #ifndef __ASSEMBLY__
  
-#define IS_ERR_VALUE(x) unlikely((unsigned long)(void *)(x) >= (unsigned long)-MAX_ERRNO)
+#define IS_ERR_VALUE(x) unlikely(is_error_check(x))
+
+static inline int is_error_check(unsigned long error)

Please leave the existing macro alone. I think you were looking for
something specific to the return code of qe_muram_alloc() function,
so please add a helper in that subsystem if you need it, not in
the generic header files.

qe_muram_alloc (a.k.a. cpm_muram_alloc) returns unsigned long.  The
problem is certain callers that store the return value in a u32.  Why
not just fix those callers to store it in unsigned long (at least until
error checking is done)?

Yes, that would also address another problem with code like

          kfree((void *)ugeth->tx_bd_ring_offset[i]);

which is not 64-bit safe when tx_bd_ring_offset is a 32-bit value
that also holds the return value of qe_muram_alloc.

Well, hopefully it doesn't hold a return of qe_muram_alloc() when it's
being passed to kfree()...

There's also the code that casts kmalloc()'s return to u32, etc.
ucc_geth is not 64-bit clean in general.

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	Arnd

Yes, we will fix caller. Caller api is not safe on 64bit.

The API is fine (or at least, I haven't seen a valid issue pointed out
yet).  The problem is the ucc_geth driver.

quoted

Even qe_muram_addr(a.k.a. cpm_muram_addr )passing value unsigned int,
but it should be unsigned long.

cpm_muram_addr takes unsigned long as a parameter, not that it matters
since you can't pass errors into it and a muram offset should never
exceed 32 bits.

-Scott

Yes, It will work for 32bit machine. But will not safe for 64bit.

Example :
ugeth->tx_bd_ring_offset[j] =
     qe_muram_alloc(length  UCC_GETH_TX_BD_RING_ALIGNMENT);
if (!IS_ERR_VALUE(ugeth->tx_bd_ring_offset[j]))
    ugeth->p_tx_bd_ring[j] =
    (u8 __iomem *) qe_muram_addr(ugeth-> tx_bd_ring_offset[j]);

If qe_muram_alloc will return any error,  IS_ERR_VALUE will
always return 0 (IS_ERR_VALUE will always pass for 'unsigned int').
Now qe_muram_addr will return wrong virtual address. Which
can cause an error.

-Arvind