On 01/24/2014 01:24 PM, Al Viro wrote:
> On Fri, Jan 24, 2014 at 11:21:26AM +0100, Denys Vlasenko wrote:
>> If given buffer size is zero, we forget to rcu_read_unlock()
>> on error path.
>
> Er... Where could we ever get called with size zero? IOW, the
> real question is whether that check makes any sense. If nothing
> else, a much more obvious fix (again, assuming there is a call
> chain that could have triggered that in the first place), would
> be to take that
> if (buflen < 1)
> goto Elong;
> on the very top of __dentry_path(). Note that buflen never
> change, so this check could bloody well be handled once - and
> earlier.
Yes. In fact the check is buggier than I thought:
prepend(&end, &len, "\0", 1);
if (buflen < 1)
goto Elong;
/* Get '/' right */
retval = end-1;
*retval = '/'; <=== !!!
It should be "buflen < 2". With buflen == 1, we touch buffer[-1].
> But again, the callers shouldn't be calling it that
> way...
I'll add a check in d_path() and post another patch.
I assume the assertion should be 'size >= 2', since
path "" should never be produced anyway, the shortest path
is "/"?
--
vda
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