On Mon, Jul 16, 2018 at 1:25 PM, Andrey Konovalov andreyknvl@google.com wrote:
So the checker reports ~100 different places where a __user pointer being casted. I've looked through them and found 3 places where we need to add untagging. Source code lines below come from 4.18-rc2+ (6f0d349d).
Place 1:
arch/arm64/mm/fault.c:302:34: warning: user pointer cast current->thread.fault_address = (unsigned long)info->si_addr;
Compare a pointer with TASK_SIZE (1 << 48) to check whether it lies in the kernel or in user space. Need to untag the address before performing a comparison.
Place 2:
fs/namespace.c:2736:21: warning: user pointer cast size = TASK_SIZE - (unsigned long)data;
A similar check performed by subtracting a pointer from TASK_SIZE. Need to untag before subtracting.
Place 3:
drivers/usb/core/devio.c:1407:29: warning: user pointer cast unsigned long uurb_start = (unsigned long)uurb->buffer; drivers/usb/core/devio.c:1636:31: warning: user pointer cast unsigned long uurb_start = (unsigned long)uurb->buffer; drivers/usb/core/devio.c:1715:30: warning: user pointer cast unsigned long uurb_start = (unsigned long)uurb->buffer;
The device keeps list of mmapped areas and searches them for provided __user pointer. Need to untag before searching.
There are also a few cases of memory syscalls operating on __user pointers instead of unsigned longs like mmap:
ipc/shm.c:1355:23: warning: user pointer cast unsigned long addr = (unsigned long)shmaddr; ipc/shm.c:1566:23: warning: user pointer cast unsigned long addr = (unsigned long)shmaddr; mm/migrate.c:1586:10: warning: user pointer cast addr = (unsigned long)p; mm/migrate.c:1660:24: warning: user pointer cast unsigned long addr = (unsigned long)(*pages);
If we don't add untagging to mmap, we probably don't need it here.
The rest of reported places look fine as is. Full annotated results of running the checker are here [2].
I'll add the 3 patches with fixes to v5 of this patchset.
Catalin, WDYT?
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