Fix zero length sys_cacheflush

Fix zero length sys_cacheflush

[Atsushi Nemoto]

I found cacheflush(0, 0, 0) will crash the system.

This is because flush_icache_range(start, end) tries to flushing whole
address space (0 - ffffffff) if both start and end are zero (at least
in c-r4k.c).

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>

diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -56,6 +56,8 @@ EXPORT_SYMBOL(_dma_cache_inv);
 asmlinkage int sys_cacheflush(unsigned long __user addr,
 	unsigned long bytes, unsigned int cache)
 {
+	if (bytes == 0)
+		return 0;
 	if (!access_ok(VERIFY_WRITE, (void __user *) addr, bytes))
 		return -EFAULT;
 

Re: Fix zero length sys_cacheflush

[Ralf Baechle]

On Wed, Oct 19, 2005 at 07:57:14PM +0900, Atsushi Nemoto wrote:

> I found cacheflush(0, 0, 0) will crash the system.
> 
> This is because flush_icache_range(start, end) tries to flushing whole
> address space (0 - ffffffff) if both start and end are zero (at least
> in c-r4k.c).

Applied,

  Ralf

Re: Fix zero length sys_cacheflush

[Atsushi Nemoto]

>>>>> On Wed, 19 Oct 2005 14:29:02 +0100, Ralf Baechle <ralf@linux-mips.org> said:

>> I found cacheflush(0, 0, 0) will crash the system.
>> 
>> This is because flush_icache_range(start, end) tries to flushing
>> whole address space (0 - ffffffff) if both start and end are zero
>> (at least in c-r4k.c).

ralf> Applied,

Thanks.

BTW, sparse complains for this "unsigned long __user addr".

asmlinkage int sys_cacheflush(unsigned long __user addr,
	unsigned long bytes, unsigned int cache)

/work/git/linux-mips/arch/mips/mm/cache.c:59:7: warning: dereference of noderef expression

I suppose the "unsigned long __user addr" means that the "addr"
variable itself is an userspace object.  So its usage is wrong, isn't
it?

---
Atsushi Nemoto

Re: Fix zero length sys_cacheflush

[Ralf Baechle]

On Wed, Oct 19, 2005 at 11:22:22PM +0900, Atsushi Nemoto wrote:

> BTW, sparse complains for this "unsigned long __user addr".
> 
> asmlinkage int sys_cacheflush(unsigned long __user addr,
> 	unsigned long bytes, unsigned int cache)
> 
> /work/git/linux-mips/arch/mips/mm/cache.c:59:7: warning: dereference of noderef expression
> 
> I suppose the "unsigned long __user addr" means that the "addr"
> variable itself is an userspace object.  So its usage is wrong, isn't
> it?

It didn't complain about this use in the past.  Anyway, time to do another
pass with sparse over the code; sparse developers have invented alot of new
creative warnings ;-)

  Ralf