Le 23/12/2021 à 11:21, Kefeng Wang a écrit :

This reverts commit 517e1fbeb65f5eade8d14f46ac365db6c75aea9b.

   usercopy: Kernel memory exposure attempt detected from SLUB object not in SLUB page?! (offset 0, size 1048)!
   kernel BUG at mm/usercopy.c:99
   ...
   usercopy_abort+0x64/0xa0 (unreliable)
   __check_heap_object+0x168/0x190
   __check_object_size+0x1a0/0x200
   dev_ethtool+0x2494/0x2b20
   dev_ioctl+0x5d0/0x770
   sock_do_ioctl+0xf0/0x1d0
   sock_ioctl+0x3ec/0x5a0
   __se_sys_ioctl+0xf0/0x160
   system_call_exception+0xfc/0x1f0
   system_call_common+0xf8/0x200

When run ethtool eth0, the BUG occurred, the code shows below,

   data = vzalloc(array_size(gstrings.len, ETH_GSTRING_LEN));
   copy_to_user(useraddr, data, gstrings.len * ETH_GSTRING_LEN))

The data is alloced by vmalloc(),  virt_addr_valid(ptr) will return true
on PowerPC64, which leads to the panic, add back the is_vmalloc_or_module()
check to fix it.

Is it expected that virt_addr_valid() returns true on PPC64 for 
vmalloc'ed memory ? If that's the case it also means that 
CONFIG_DEBUG_VIRTUAL won't work as expected either.

If it is unexpected, I think you should fix PPC64 instead of adding this 
hack back. Maybe the ARM64 fix can be used as a starting point, see 
commit 68dd8ef32162 ("arm64: memory: Fix virt_addr_valid() using 
__is_lm_address()")

In the meantime, can you provide more information on your config, 
especially which memory model is used ?

Christophe