| From ffa0b64e3be58519ae472ea29a1a1ad681e32f48 Mon Sep 17 00:00:00 2001 |
| From: Kefeng Wang <wangkefeng.wang@huawei.com> |
| Date: Thu, 7 Apr 2022 00:57:57 +1000 |
| Subject: powerpc: Fix virt_addr_valid() for 64-bit Book3E & 32-bit |
| |
| From: Kefeng Wang <wangkefeng.wang@huawei.com> |
| |
| commit ffa0b64e3be58519ae472ea29a1a1ad681e32f48 upstream. |
| |
| mpe: On 64-bit Book3E vmalloc space starts at 0x8000000000000000. |
| |
| Because of the way __pa() works we have: |
| __pa(0x8000000000000000) == 0, and therefore |
| virt_to_pfn(0x8000000000000000) == 0, and therefore |
| virt_addr_valid(0x8000000000000000) == true |
| |
| Which is wrong, virt_addr_valid() should be false for vmalloc space. |
| In fact all vmalloc addresses that alias with a valid PFN will return |
| true from virt_addr_valid(). That can cause bugs with hardened usercopy |
| as described below by Kefeng Wang: |
| |
| When running ethtool eth0 on 64-bit Book3E, a BUG occurred: |
| |
| 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 |
| |
| 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 64-bit Book3E, which leads to the panic. |
| |
| As commit 4dd7554a6456 ("powerpc/64: Add VIRTUAL_BUG_ON checks for __va |
| and __pa addresses") does, make sure the virt addr above PAGE_OFFSET in |
| the virt_addr_valid() for 64-bit, also add upper limit check to make |
| sure the virt is below high_memory. |
| |
| Meanwhile, for 32-bit PAGE_OFFSET is the virtual address of the start |
| of lowmem, high_memory is the upper low virtual address, the check is |
| suitable for 32-bit, this will fix the issue mentioned in commit |
| 602946ec2f90 ("powerpc: Set max_mapnr correctly") too. |
| |
| On 32-bit there is a similar problem with high memory, that was fixed in |
| commit 602946ec2f90 ("powerpc: Set max_mapnr correctly"), but that |
| commit breaks highmem and needs to be reverted. |
| |
| We can't easily fix __pa(), we have code that relies on its current |
| behaviour. So for now add extra checks to virt_addr_valid(). |
| |
| For 64-bit Book3S the extra checks are not necessary, the combination of |
| virt_to_pfn() and pfn_valid() should yield the correct result, but they |
| are harmless. |
| |
| Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> |
| Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> |
| [mpe: Add additional change log detail] |
| Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> |
| Link: https://lore.kernel.org/r/20220406145802.538416-1-mpe@ellerman.id.au |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/powerpc/include/asm/page.h | 6 +++++- |
| 1 file changed, 5 insertions(+), 1 deletion(-) |
| |
| --- a/arch/powerpc/include/asm/page.h |
| +++ b/arch/powerpc/include/asm/page.h |
| @@ -132,7 +132,11 @@ static inline bool pfn_valid(unsigned lo |
| #define virt_to_page(kaddr) pfn_to_page(virt_to_pfn(kaddr)) |
| #define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT) |
| |
| -#define virt_addr_valid(kaddr) pfn_valid(virt_to_pfn(kaddr)) |
| +#define virt_addr_valid(vaddr) ({ \ |
| + unsigned long _addr = (unsigned long)vaddr; \ |
| + _addr >= PAGE_OFFSET && _addr < (unsigned long)high_memory && \ |
| + pfn_valid(virt_to_pfn(_addr)); \ |
| +}) |
| |
| /* |
| * On Book-E parts we need __va to parse the device tree and we can't |