Linus Torvalds 0c389d89ab maccess: make get_kernel_nofault() check for minimal type compatibility ... Now that we've renamed probe_kernel_address() to get_kernel_nofault() and made it look and behave more in line with get_user(), some of the subtle type behavior differences end up being more obvious and possibly dangerous. When you do get_user(val, user_ptr); the type of the access comes from the "user_ptr" part, and the above basically acts as val = *user_ptr; by design (except, of course, for the fact that the actual dereference is done with a user access). Note how in the above case, the type of the end result comes from the pointer argument, and then the value is cast to the type of 'val' as part of the assignment. So the type of the pointer is ultimately the more important type both for the access itself. But 'get_kernel_nofault()' may now _look_ similar, but it behaves very differently. When you do get_kernel_nofault(val, kernel_ptr); it behaves like val = *(typeof(val) *)kernel_ptr; except, of course, for the fact that the actual dereference is done with exception handling so that a faulting access is suppressed and returned as the error code. But note how different the casting behavior of the two superficially similar accesses are: one does the actual access in the size of the type the pointer points to, while the other does the access in the size of the target, and ignores the pointer type entirely. Actually changing get_kernel_nofault() to act like get_user() is almost certainly the right thing to do eventually, but in the meantime this patch adds logit to at least verify that the pointer type is compatible with the type of the result. In many cases, this involves just casting the pointer to 'void *' to make it obvious that the type of the pointer is not the important part. It's not how 'get_user()' acts, but at least the behavioral difference is now obvious and explicit. Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2020-06-18 12:10:37 -07:00
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asm	maccess: make get_kernel_nofault() check for minimal type compatibility	2020-06-18 12:10:37 -07:00
uapi/asm	Cleanup some leftover para-virtualization pieces	2019-12-04 11:05:13 -08:00