On Fri 2019-05-10 12:40:58, Steven Rostedt wrote:
On Fri, 10 May 2019 18:32:58 +0200
Martin Schwidefsky [off-list ref] wrote:
quoted
On Fri, 10 May 2019 12:24:01 -0400
Steven Rostedt [off-list ref] wrote:
quoted
On Fri, 10 May 2019 10:42:13 +0200
Petr Mladek [off-list ref] wrote:
quoted
static const char *check_pointer_msg(const void *ptr)
{
- char byte;
-
if (!ptr)
return "(null)";
- if (probe_kernel_address(ptr, byte))
+ if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
return "(efault)";
< PAGE_SIZE ?
do you mean: < TASK_SIZE ?
The check with < TASK_SIZE would break on s390. The 'ptr' is
in the kernel address space, *not* in the user address space.
Remember s390 has two separate address spaces for kernel/user
the check < TASK_SIZE only makes sense with a __user pointer.
So we allow this to read user addresses? Can't that cause a fault?
I did some quick check and did not found anywhere a user pointer
being dereferenced via vsprintf().
In each case, %s did the check (ptr < PAGE_SIZE) even before this
patchset. The other checks are in %p format modifiers that are
used to print various kernel structures.
Finally, it accesses the pointer directly. I am not completely sure
but I think that it would not work that easily with an address
from the user address space.
Best Regards,
Petr