Re: [PATCH] Revert "mm/usercopy: Drop extra is_vmalloc_or_module() check"
From: Kefeng Wang
Date: Fri Dec 24 2021 - 21:05:28 EST
On 2021/12/24 21:18, Christophe Leroy wrote:
Le 24/12/2021 à 08:06, Kefeng Wang a écrit :
On 2021/12/24 14:01, Christophe Leroy wrote:
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.
Our product reports this bug to me, after let them do some test,
I found virt_addr_valid return true for vmalloc'ed memory on their board.
I think DEBUG_VIRTUAL could not be work well too, but I can't test it.
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()")
Yes， I check the history, fix virt_addr_valid() on PowerPC is what I
firstly want to do,
but I am not familiar with PPC, and also HARDENED_USERCOPY on other's
ARCHs could
has this issue too, so I add the workaround back.
1) PPC maintainer/expert, any suggestion ?
2) Maybe we could add some check to WARN this scenario.
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -229,6 +229,8 @@ static inline void check_heap_object(const void
*ptr, unsigned long n,
if (!virt_addr_valid(ptr))
return;
+ WARN_ON_ONCE(is_vmalloc_or_module_addr(ptr));
In the meantime, can you provide more information on your config,
especially which memory model is used ?
Some useful configs,
CONFIG_PPC64=y
CONFIG_PPC_BOOK3E_64=y
CONFIG_E5500_CPU=y
CONFIG_TARGET_CPU_BOOL=y
CONFIG_PPC_BOOK3E=y
CONFIG_E500=y
CONFIG_PPC_E500MC=y
CONFIG_PPC_FPU=y
CONFIG_FSL_EMB_PERFMON=y
CONFIG_FSL_EMB_PERF_EVENT=y
CONFIG_FSL_EMB_PERF_EVENT_E500=y
CONFIG_BOOKE=y
CONFIG_PPC_FSL_BOOK3E=y
CONFIG_PTE_64BIT=y
CONFIG_PHYS_64BIT=y
CONFIG_PPC_MMU_NOHASH=y
CONFIG_PPC_BOOK3E_MMU=y
CONFIG_SELECT_MEMORY_MODEL=y
CONFIG_FLATMEM_MANUAL=y
CONFIG_FLATMEM=y
CONFIG_FLAT_NODE_MEM_MAP=y
CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
OK so it is PPC64 book3e and with flatmem.
The problem is virt_to_pfn() which uses __pa()
__pa(x) on PPC64 is (x) & 0x0fffffffffffffffUL
And on book3e/64 we have
VMALLOC_START = KERN_VIRT_START = ASM_CONST(0x8000000000000000)
It means that __pa() will return a valid PFN for VMALLOCed addresses.
So an additional check is required in virt_addr_valid(), maybe check
that (kaddr & PAGE_OFFSET) == PAGE_OFFSET
Can you try that ?
#define virt_addr_valid(kaddr) ((kaddr & PAGE_OFFSET) == PAGE_OFFSET &&
pfn_valid(virt_to_pfn(kaddr)))
I got this commit,
commit 4dd7554a6456d124c85e0a4ad156625b71390b5c
Author: Nicholas Piggin <npiggin@xxxxxxxxx>
Date: Wed Jul 24 18:46:37 2019 +1000
powerpc/64: Add VIRTUAL_BUG_ON checks for __va and __pa addresses
Ensure __va is given a physical address below PAGE_OFFSET, and __pa is
given a virtual address above PAGE_OFFSET.
It has check the PAGE_OFFSET in __pa, will test it and resend the
patch(with above warning changes).
Thanks.
Thanks
Christophe