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Kernel: Assert that copy_to/from_user() are called with user addresses
This will panic the kernel immediately if these functions are misused so we can catch it and fix the misuse. This patch fixes a couple of misuses: - create_signal_trampolines() writes to a user-accessible page above the 3GB address mark. We should really get rid of this page but that's a whole other thing. - CoW faults need to use copy_from_user rather than copy_to_user since it's the *source* pointer that points to user memory. - Inode faults need to use memcpy rather than copy_to_user since we're copying a kernel stack buffer into a quickmapped page. This should make the copy_to/from_user() functions slightly less useful for exploitation. Before this, they were essentially just glorified memcpy() with SMAP disabled. :^)
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6 changed files with 33 additions and 15 deletions
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@ -214,3 +214,10 @@ inline bool is_user_address(VirtualAddress vaddr)
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{
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return vaddr.get() < 0xc0000000;
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}
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inline bool is_user_range(VirtualAddress vaddr, size_t size)
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{
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if (vaddr.offset(size) < vaddr)
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return false;
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return is_user_address(vaddr) && is_user_address(vaddr.offset(size));
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}
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