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Kernel: Assert that copy_to/from_user() are called with user addresses

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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. :^)
This commit is contained in:
Andreas Kling 2020-01-19 09:14:14 +01:00
parent 2cd212e5df
commit f7b394e9a1
6 changed files with 33 additions and 15 deletions
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6
Kernel/StdLib.h
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@ -42,9 +42,9 @@ extern "C" {
static_assert(sizeof(size_t) == 4);
void* copy_to_user(void*, const void*, size_t);
void* copy_from_user(void*, const void*, size_t);
void* memset_user(void*, int, size_t);
void copy_to_user(void*, const void*, size_t);
void copy_from_user(void*, const void*, size_t);
void memset_user(void*, int, size_t);
void* memcpy(void*, const void*, size_t);
char* strcpy(char*, const char*);